Who wrote the first 5 books in the Bible?

The books themselves claim to have been written by Moses, and there are portions of Genesis that Moses was a compiler of early documents or as some believe wrote down the memorized oral tradition (Gen.1-10). Genesis means origin or source. The “Generations of” the family documents, genealogical lines, the expansion of sin through early history and the judgment of God. (Lev.1:1-2; Num.33:2 Deut.1:1 Ex.17:14). The narrative of Genesis is structured by the phrase that These are the generations which occurs ten times “ [Generations- toledot, “family histories”]

What God told Moses he wrote. He did not write anything God did not have him to write.

Exodus 24:4: “And Moses wrote all the words of the LORD. And he rose early in the morning, and built an altar at the foot of the mountain, and twelve pillars according to the twelve tribes of Israel.”

Exodus 34:27-28 Then the LORD said to Moses, “Write these words, for according to the tenor of these words I have made a covenant with you and with Israel.” So he was there with the LORD forty days and forty nights; he neither ate bread nor drank water. And He wrote on the tablets the words of the covenant, the Ten Commandments.” I

(Ex. 24:4,7; 34:27-28; Nu. 33:2; De. 1:1-5; 4:4-5; 31:9-12,24-26). If Moses did not write the Pentateuch, the Bible is inaccurate from its beginning. (Joshua 1:7; 8:30-35; Judges 3:4; 1 Ki. 2:3; 2 Ki. 14:6; 22:8-11; 23:21-25; Ezra 3:2; Neh. 8:1; 9:14; Dan. 9:11; Mal. 4:4; Mark 12:19 )

The books of Genesis, Leviticus, and Deuteronomy, are separate units which collectively are called the Pentateuch penta, “five;” teuchos, “a tool” or “implement,”  the five-fold book.

Then we have testimony of the New Testament. The apostles said that ‘Moses wrote unto us’ (Mark 12:19) as did the apostle Paul, who when speaking of a passage in the Pentateuch said, ‘Moses describeth’ (Romans 10:5).

The issue as to the authorship of the first five books is also enforced by the testimony of the Jesus Christ. Jesus made it clear that Moses wrote these books (Mark 7:10; 10:3–5; 12:26; Luke 2:22,5:14; 16:29–31; 24:27, 44; John 7:19, 23). Jesus Christ quoted from every part of the Pentateuch (5 books) and attributed the authorship to Moses: Genesis (Mt. 19:4-6; 24:37-39); Exodus (Mk. 12:26 citing Ex. 3:6); Leviticus (Mt. 8:4 citing Lev. 14:1-32); Numbers (Jn. 3:14-15 citing Num. 21:8,9 and Jn. 6:31-32 citing Num. 11:6-9); Deuteronomy (Mk. 10:4-5 citing Deut. 24:1).

The early church, believed Moses was the author, the Jerusalem Talmud and the first century Jewish historian Josephus.

John 1:17 For the law was given through Moses” So he is attributed to be the author of the law which is found ion Leviticus and Deuteronomy).

Jesus refers to Moses in marriage that is established in the beginning of Genesis. Mark 10:3-8 “What did Moses command you?” They said, “Moses permitted a man to write a certificate of divorce, and to dismiss her.” And Jesus answered and said to them, “Because of the hardness of your heart he wrote you this precept. But from the beginning of the creation, God 'made them male and female.' 'For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh'; so then they are no longer two, but one flesh.”

John 8:4-5 They said to Him, “Teacher, this woman was caught in adultery, in the very act. Now Moses , in the law, commanded us that such should be stoned.”

Numbers 33:2-3 “Now Moses wrote down the starting points of their journeys at the command of the LORD. And these are their journeys according to their starting points”

Deuteronomy 31:9: “So Moses wrote this law and delivered it to the priests”

John 5:46-47 “For if you believed Moses, you would believe Me; for he wrote about Me. But if you do not believe his writings, how will you believe My words?”

When did Moses write about Jesus? In Gen.3:15 when the prophecy of the Messiah was first given. Also when Jesus spoke of “And as Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up” John 3:14)

Mark 12:26-27 ‘But concerning the dead, that they rise, have you not read in the book of Moses , in the burning bush passage, how God spoke to him, saying, 'I am the God of Abraham, the God of Isaac, and the God of Jacob'? 27 He is not the God of the dead, but the God of the living. You are therefore greatly mistaken.”

Here Jesus does not cite book of Exodus but calls it the book of Moses. There are many more examples like this.

Luke 16:31: But he said to him, 'If they do not hear Moses and the prophets, neither will they be persuaded though one rise from the dead.' “

Luke 24:27:And beginning at Moses and all the Prophets, He expounded to them in all the Scriptures the things concerning Himself. “

Moses authored the book until he died (chapter 34 of Deuteronomy).

Deuteronomy 31:24: “Moses made an end of writing the words of this law in a book” the whole Pentateuch. Joshua is told to continue the writing. The Old Testament books have numerous references to the laws, history, of the Pentateuch they are universally accepted as words of Moses.