The Sabbath was instituted in the garden of Eden and there is no indication it was not kept in the book of Genesis. It is strongly reaffirmed in the remainder of the Old Testament (The Fourth Commandment says "Remember the Sabbath....," the people being commanded to keep it and being assured of blessings if they did. Christ taught and personally kept the Sabbath while He was on earth. The Early Church continued to keep the Seventh-day Sabbath after Christ's death, and was predicted by Christ to still be keeping the Sabbath at the time of the fall of Jerusalem
Genesis 2:2-3 (KJV) "And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made. 3 And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made."
"Exodus 20:8 (KJV) "Remember the sabbath day, to keep it holy." (The Sabbath was known prior to the giving the commandments since they were told to "remember" the Sabbath.)
Exodus 31:12-17 (KJV) "And the Lord spake unto Moses, saying, 13 Speak thou also unto the children of Israel, saying, Verily my sabbaths ye shall keep: for it is a sign between me and you throughout your generations; that ye may know that I am the Lord that doth sanctify you. 14 Ye shall keep the sabbath therefore; for it is holy unto you: every one that defileth it shall surely be put to death: for whosoever doeth any work therein, that soul shall be cut off from among his people. 15 Six days may work be done; but in the seventh is the sabbath of rest, holy to the Lord: whosoever doeth any work in the sabbath day, he shall surely be put to death. 16 Wherefore the children of Israel shall keep the sabbath, to observe the sabbath throughout their generations, for a perpetual covenant. 17 It is a sign between me and the children of Israel for ever: for in six days the Lord made heaven and earth, and on the seventh day he rested, and was refreshed."
"Ezekiel 20:12 (KJV) "Moreover also I gave them my sabbaths, to be a sign between me and them, that they might know that I am the Lord that sanctify them."
"Exodus 16:23-26 (KJV) "And he said unto them, This is that which the Lord hath said, To morrow is the rest of the holy sabbath unto the Lord: bake that which ye will bake to day, and seethe that ye will seethe; and that which remaineth over lay up for you to be kept until the morning. 24 And they laid it up till the morning, as Moses bade: and it did not stink, neither was there any worm therein. 25 And Moses said, Eat that to day; for to day is a sabbath unto the Lord: to day ye shall not find it in the field. 26 Six days ye shall gather it; but on the seventh day, which is the sabbath, in it there shall be none."
Exodus 16:27-30 (KJV) "And it came to pass, that there went out some of the people on the seventh day for to gather, and they found none. 28 And the Lord said unto Moses, How long refuse ye to keep my commandments and my laws? 29 See, for that the Lord hath given you the sabbath, therefore he giveth you on the sixth day the bread of two days; abide ye every man in his place, let no man go out of his place on the seventh day. 30 So the people rested on the seventh day."
Deuteronomy 5:15 (KJV) "And remember that thou wast a servant in the land of Egypt, and that the Lord thy God brought thee out thence through a mighty hand and by a stretched out arm: therefore the Lord thy God commanded thee to keep the sabbath day."
Jeremiah 17:21-25 (KJV) "Thus saith the Lord; Take heed to yourselves, and bear no burden on the sabbath day, nor bring it in by the gates of Jerusalem; 22 Neither carry forth a burden out of your houses on the sabbath day, neither do ye any work, but hallow ye the sabbath day, as I commanded your fathers. 23 But they obeyed not, neither inclined their ear, but made their neck stiff, that they might not hear, nor receive instruction. 24 And it shall come to pass, if ye diligently hearken unto me, saith the Lord, to bring in no burden through the gates of this city on the sabbath day, but hallow the sabbath day, to do no work therein; 25 Then shall there enter into the gates of this city kings and princes sitting upon the throne of David, riding in chariots and on horses, they, and their princes, the men of Judah, and the inhabitants of Jerusalem: and this city shall remain for ever."
Nehemiah 13:15-16 (KJV) "In those days saw I in Judah some treading wine presses on the sabbath, and bringing in sheaves, and lading asses; as also wine, grapes, and figs, and all manner of burdens, which they brought into Jerusalem on the sabbath day: and I testified against them in the day wherein they sold victuals. 16 There dwelt men of Tyre also therein, which brought fish, and all manner of ware, and sold on the sabbath unto the children of Judah, and in Jerusalem."
Nehemiah 13:19-22 (KJV) "And it came to pass, that when the gates of Jerusalem began to be dark before the sabbath, I commanded that the gates should be shut, and charged that they should not be opened till after the sabbath: and some of my servants set I at the gates, that there should no burden be brought in on the sabbath day. 20 So the merchants and sellers of all kind of ware lodged without Jerusalem once or twice. 21 Then I testified against them, and said unto them, Why lodge ye about the wall? if ye do so again, I will lay hands on you. From that time forth came they no more on the sabbath. 22 And I commanded the Levites that they should cleanse themselves, and that they should come and keep the gates, to sanctify the sabbath day. Remember me, O my God, concerning this also, and spare me according to the greatness of thy mercy."
Jeremiah 17:27 (KJV) "But if ye will not hearken unto me to hallow the sabbath day, and not to bear a burden, even entering in at the gates of Jerusalem on the sabbath day; then will I kindle a fire in the gates thereof, and it shall devour the palaces of Jerusalem, and it shall not be quenched."
Isaiah 56:2 (KJV) "Blessed is the man that doeth this, and the son of man that layeth hold on it; that keepeth the sabbath from polluting it, and keepeth his hand from doing any evil."
Isaiah 58:13-14 (KJV) "If thou turn away thy foot from the sabbath, from doing thy pleasure on my holy day; and call the sabbath a delight, the holy of the Lord, honourable; and shalt honour him, not doing thine own ways, nor finding thine own pleasure, nor speaking thine own words: 14 Then shalt thou delight thyself in the Lord; and I will cause thee to ride upon the high places of the earth, and feed thee with the heritage of Jacob thy father: for the mouth of the Lord hath spoken it."
Mark 2:28 "Therefore the Son of man is Lord also of the sabbath."
“Wherefore the Son of man is Lord also of the Sabbath.” These words are full of instruction and comfort. Because the Sabbath was made for man, it is the Lord’s day. It belongs to Christ. For “all things were made by Him; and without Him was not anything made that was made.” John 1:3. Since He made all things, He made the Sabbath. By Him it was set apart as a memorial of the work of creation. It points to Him as both the Creator and the Sanctifier. It declares that He who created all things in heaven and in earth, and by whom all things hold together, is the head of the church, and that by His power we are reconciled to God. For, speaking of Israel, He said, “I gave them My Sabbaths, to be a sign between Me and them, that they might know that I am the Lord that sanctify them,”—make them holy. Ezekiel 20:12. Then the Sabbath is a sign of Christ’s power to make us holy. And it is given to all whom Christ makes holy. As a sign of His sanctifying power, the Sabbath is given to all who through Christ become a part of the Israel of God. {DA 288.2}
Luke 4:16 "And he came to Nazareth, where he had been brought up: and, as his custom was, he went into the synagogue on the sabbath day, and stood up for to read."
Matthew 24:20 "But pray ye that your flight be not in the winter, neither on the sabbath day:"
Luke 4:31 "And came down to Capernaum, a city of Galilee, and taught them on the sabbath days."
Luke 6:6 "And it came to pass also on another sabbath, that he entered into the synagogue and taught: and there was a man whose right hand was withered."
John 5:5-9 "And a certain man was there, which had an infirmity thirty and eight years. 6 When Jesus saw him lie, and knew that he had been now a long time in that case, he saith unto him, Wilt thou be made whole? 7 The impotent man answered him, Sir, I have no man, when the water is troubled, to put me into the pool: but while I am coming, another steppeth down before me. 8 Jesus saith unto him, Rise, take up thy bed, and walk. 9 And immediately the man was made whole, and took up his bed, and walked: and on the same day was the sabbath."
Mark 3:1-5 "And he entered again into the synagogue; and there was a man there which had a withered hand. 2 And they watched him, whether he would heal him on the sabbath day; that they might accuse him. 3 And he saith unto the man which had the withered hand, Stand forth. 4 And he saith unto them, Is it lawful to do good on the sabbath days, or to do evil? to save life, or to kill? But they held their peace. 5 And when he had looked round about on them with anger, being grieved for the hardness of their hearts, he saith unto the man, Stretch forth thine hand. And he stretched it out: and his hand was restored whole as the other."
Luke 13:16 "And ought not this woman, being a daughter of Abraham, whom Satan hath bound, lo, these eighteen years, be loosed from this bond on the sabbath day?"
Luke 23:54-56 "And that day was the preparation, and the sabbath drew on. 55 And the women also, which came with him from Galilee, followed after, and beheld the sepulchre, and how his body was laid. 56 And they returned, and prepared spices and ointments; and rested the sabbath day according to the commandment."
Mark 16:1-2 "And when the sabbath was past, Mary Magdalene, and Mary the mother of James, and Salome, had bought sweet spices, that they might come and anoint him. 2 And very early in the morning the first day of the week, they came unto the sepulchre at the rising of the sun."
Acts 13:14 "But when they departed from Perga, they came to Antioch in Pisidia, and went into the synagogue on the sabbath day, and sat down."
Acts 13:42-44 "And when the Jews were gone out of the synagogue, the Gentiles besought that these words might be preached to them the next sabbath. 43 Now when the congregation was broken up, many of the Jews and religious proselytes followed Paul and Barnabas: who, speaking to them, persuaded them to continue in the grace of God. 44 And the next sabbath day came almost the whole city together to hear the word of God."
Acts 16:12-13 "And from thence to Philippi, which is the chief city of that part of Macedonia, and a colony: and we were in that city abiding certain days. 13 And on the sabbath we went out of the city by a river side, where prayer was wont to be made; and we sat down, and spake unto the women which resorted thither."
Acts 17:2 "And Paul, as his manner was, went in unto them, and three sabbath days reasoned with them out of the scriptures,"
Acts 18:4 "And he reasoned in the synagogue every sabbath, and persuaded the Jews and the Greeks."
Acts 18:11 "And he continued there a year and six months, teaching the word of God among them."
Acts 28:17 "And it came to pass, that after three days Paul called the chief of the Jews together: and when they were come together, he said unto them, Men and brethren, though I have committed nothing against the people, or customs of our fathers, yet was I delivered prisoner from Jerusalem into the hands of the Romans."
Acts 15:21 "For Moses of old time hath in every city them that preach him, being read in the synagogues every sabbath day."
Acts 13:42-44 (KJV) 42 And when the Jews were gone out of the synagogue, the Gentiles besought that these words might be preached to them the next sabbath. ... 44 And the next sabbath day came almost the whole city together to hear the word of God."
Isaiah 66:22-23 "For as the new heavens and the new earth, which I will make, shall remain before me, saith the Lord, so shall your seed and your name remain. 23 And it shall come to pass, that from one new moon to another, and from one sabbath to another, shall all flesh come to worship before me, saith the Lord."