The physical appearance of Ishaq (peace be upon him)

It is narrated from Ka'b al-Ahbar (may Allah have mercy on him) that he said: "Then came Ishaq bin Ibrahim (peace be upon them both), whom Allah Almighty made a light, a radiance and a coolness of the eyes for his parents. He was the most handsome of people in face, the most beautiful, and the finest in speech. He was fair-skinned, with curly hair and beard, and he resembled Ibrahim (peace be upon him) in his outward form and his inner character (manners). Then Ya'qub and Aysa were born to Ishaq. Of the two, Ya'qub was the more handsome, the more eloquent, and the more beautiful and refined, while Aysa had much hair on his body, face and head, and he settled in Rum (the Byzantine lands), as Sayyiduna Samurah bin Jundub (may Allah be pleased with him) narrated."

It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) concerning the saying of Allah Almighty: 'And We gave him glad tidings of Ishaq' [Surah al-Saffat: 112], that he said: "This was the glad tidings of prophethood. He was given glad tidings of Ishaq (peace be upon him) twice: once when he was born, and a second time when he was made a prophet."
The chain of this hadith is sahih (authentic), but the two Shaykhs did not record it.
Mention of those who said that the one to be sacrificed (al-Dhabih) was Ishaq bin Ibrahim (peace be upon them both).