The son bound in the biblical story read on Rosh Hashanah’s second day is Isaac.
Genesis 22 recounts Abraham’s test: he is told to take Isaac to Moriah and offer him as a sacrifice. Isaac is bound on the altar, but an angel intervenes before Abraham harms him. Abraham then sacrifices a ram, which has been caught by its horns in nearby thorns.
In traditional Jewish synagogue practice, the Akedah is read on the second day of Rosh Hashanah, while the first day’s reading focuses on the birth and early life of Isaac. The reading is not a story about Joseph, Jacob, or Ishmael, although all three are important figures in Genesis. Ishmael is Abraham’s older son with Hagar, but Isaac is the son named in the Binding narrative. The episode’s ram also helps explain the long-standing association between the story and the sound of the shofar.