The 10 commandments were given to Moses at Mount Sinae about 1300 years BC. The exact date is not known.
About 600,000 men at Mount Sinae chose to accept the commandments and entered into a covenant with God.
The covenant is a contract. Males who chose God entered into the covenant with God by circumcising male children 7 days after birth.
Thus, was born the Jewish people.
They chose God. God did not choose them.