This atheist teaches nothing. Such a claim only shows your ignorance, about Atheism and the old testament.
There in one and only one rule for one to be an atheist IE a disbelief in god(s). There are no such things as atheist teachings
The 613 commandments (mitzvah) are all contained in the Torah .aka the pentateuch, the firsts five books of the Old Testament . IE Genesis, Exodus, Leviticus, Numbers and Deuteronomy . They are known collectively as the mitzvot and all are part of The Law claimed to have been revealed to Moses.
Read and be informed:
Mitzvot
There are 613 mitzvot, which are Jewish rules or commandments. They cover many issues, including instructions about food, punishments and how God should be worshipped.
Jews agreed to follow these rules when they were given to Moses as part of the covenant. Following these laws is a core part of Jewish identity for many Jews.
The mitzvot can be read as a continuous list in the Mishneh Torah, written by Moses Maimonides . Maimonides was a Jewish philosopher who contributed to Jewish understanding and interpretation of the Torah.
This link lists them all. To be fair, many are no longer kept: Eg people are no longer stoned for adultery, fathers no longer kill recalcitrant children or sell their daughters into slavery. Each of those things are included in the Law of Moses.
That such are no longer practiced gives the lie to the claim that god’s laws are for all time.
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Jesus is reported as saying he had not come to change the law. Nor did he. The changes which removed pretty much all ritual commandments was made by Saul of Tarsus following his hallucinations.
Matthew 15:17-18 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil. For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
All was not fulfilled because Jesus failed to keep his promise to return:
Matthew 16:28.Verily I say unto you, There be some standing here, which shall not taste of death, till they see the Son of man coming in his kingdom.
Pretty sure he made the same promise elsewhere in the gospels, but I forget where.
His followers expected Jesus to return within their lifetime. When he did not, the religion we call christianity became just another failed millenarian movement.