Ar: Ishaq, Ishak.
Heb: Yitschaq
(
The second son of Abraham, younger brother of Ishmael. Isaac's mother is Sarah and Ishmael's Hagar.
The main controversy about Isaac is Abraham's sacrifices of his son.
The following articles go into great detail:
Abraham and the Child of Sacrifice - Isaac or Ishmael?
The Sacrifice Of Abraham: Isaac or Ishmael?
Isaac is mentioned in the Qur'an in these passages: