Tafsir of As-Saffat 37:111

And We left for him among the later generations. "Salam (peace!) be upon Ibrahim!'' Thus indeed do We reward the doers of good. Verily, he was one of Our believing servants. Ibn Ishaq said, "I heard Muhammad bin Ka`b Al-Qurazi say, `The one whom Allah commanded Ibrahim to sacrifice of his two sons was Ismail.' We find this in the Book of Allah, because when Allah finishes the story of the one of the two sons of Ibrahim who was to be sacrificed, He then says:

وبشرناه بٳسحق نبيا من الصالحين