What did Moses contribute to Judaism after his meeting with God on Mount Sinai?

Answer 1

From that meeting, Moses brought down the 10 commandments from God. Of course he saw the Jews worshipping false idols (the Golden Calf) and he smashed the first set in a rage, but that's a different story.

Answer:

Moses brought down the Two Stone Tablets with the Ten Commandments inscribed on them by God (Exodus 31:18).

After that, he taught them the entire Torah during the duration of their forty years in the wilderness. He wrote the complete Torah-scroll shortly before he died (Deuteronomy 31:24).

Answer 2

Moses achieved the highest level of prophecy (Deuteronomy ch.34) and was called upon by God to receive the Ten Commandments (Exodus ch.19-20). He went up on Mount Sinai for 40 days and nights (Deuteronomy ch.9-10) and brought down the Two Stone Tablets with the Ten Commandments (Exodus 31:18). He later received the entire Torah from God (Exodus 24:12) and recorded it in writing before he died (Deuteronomy 31:24). He brought the Israelites into the covenant with God (Exodus ch.19 and ch.24), and he oversaw the building of the Tabernacle (Exodus ch.35-40). He was the humblest of men and the greatest of prophets (Numbers ch.12).

See also:

What problems did Moses face and overcome?

The Israelites' complaints, and the Golden Calf

Moses was an Israelite, a great-great grandson of Jacob. He was born 245 years after the death of Abraham. The time when Moses was born was when the Pharaoh had ordered his people to kill all Israelite male infants because he (Pharaoh) was afraid that the Israelites would become too strong for him (Exodus ch.1-2).

Moses' mother didn't want him to die. So she made a basket for him and put him in it to float in the Nile reeds. He was found by Pharaoh's daughter, who took pity on him (Exodus ch.2) and raised him as her own son. (See: How did Moses know he was an Israelite?)

Moses was forced to flee after killing a cruel Egyptian taskmaster, and went to Midian, where he wedded the daughter of Jethro. He later brought the Israelites out of Egyptian slavery (Exodus ch.12).