In Genesis 22, God tested Abraham's faith by commanding him to offer his son Isaac as a burnt offering on Mount Moriah. Abraham obeyed and prepared the altar, bound Isaac, and raised the knife to slay him. At that critical moment, the angel of the Lord called out to Abraham from heaven, telling him not to lay his hand on the boy (Genesis 22:11-12). The angel declared that Abraham had demonstrated his fear of God by not withholding his only son.
After the angel intervened, Abraham looked up and saw a ram caught in a thicket by its horns, which he sacrificed in place of Isaac. This episode is foundational in biblical theology because it demonstrates the principle of substitutionary sacrifice and foreshadows God's provision.
The other options are incorrect: Melchizedek was a priest-king of Salem who blessed Abraham in Genesis 14, long before this event. Sarah, Isaac's mother, was not present at Mount Moriah during the sacrifice. A servant accompanied Abraham on the journey but was left at the foot of the mountain with the donkey and did not intervene.