The Old Testament Commandments are primarily enshrined in the Law of God given to Moses. These laws are found in the books of Exodus, Leviticus, Numbers and Deuteronomy. At the heart of the Law are the ten Commandments. These may be found in Exodus 20:1-17.
At the heart of the 10 commandments are the two "great commandments."
Mark 12:29-34 Jesus answered him, "The first of all the commandments is: ‘Hear, O Israel, the LORD our God, the LORD is one. 30 ‘And you shall love the LORD your God with all your heart, with all your soul, with all your mind, and with all your strength.’ This is the first commandment. 31 "And the second, like it, is this: ‘You shall love your neighbor as yourself.’ There is no other commandment greater than these." 32 So the scribe said to Him, "Well said, Teacher. You have spoken the truth, for there is one God, and there is no other but He. 33 "And to love Him with all the heart, with all the understanding, with all the soul, and with all the strength, and to love one’s neighbor as oneself, is more than all the whole burnt offerings and sacrifices." 34 Now when Jesus saw that he answered wisely, He said to him, "You are not far from the kingdom of God."
I hope you have found this helpful.