The commandment of circumcision was in place, and Abraham was circumcised,
about a year before Isaac was born. So Isaac was circumcised shortly after his
birth, with no repetition of the commandment required.
Abraham had to circumcise himself to show his loyalty to God. God in return promised the land of Canaan to his descendants given him by Sarah (i.e. Isaac) and that both Isaac and Ishmael would father nations that would be as numerous as the stars in the sky or grains of sand on the ground.
He did not kill Isaac. He showed readiness to do so if that was God's command, and God then told him that it was a test (see Genesis ch.22).
Abraham received a ram to sacrifice instead of his son Isaac. This demonstrated Abraham's faith and willingness to obey God's command.
It's in the Torah, the Jewish Bible.
The God of Abraham, Isaac, and Jacob.
Abraham offered Issac after he was commanded to in Genesis 22:2.
Isaac (Genesis ch.22). God tested Abraham's obedience by seeming to request that he sacrifice Isaac. See also:More about Abraham and Isaac
God tested Abraham's obedience by asking him to sacrifice his only son Isaac, we must remember that Abraham , got Isaac when he was 100 years old.
He took his son to the mountain because God told him to. It was a test to see if Abraham would obey God. Once there, God told Abraham to kill Isaac. As Abraham was about to kill Isaac, God said "Stop, you have proven yourself to me"!
Abraham, at Jehovah's command, attempted to offer up Isaac. It was to the land of Moriah that Abraham traveled from the vicinity of Beer-Sheba; and on the third day, he saw that divinely designated place from a distance Genesis 21:33,34 Genesis 22:4,19.
God.
The God of Abraham, Isaac, and Jacob is eternally pre-existent.