(Al-Hijr) 15 : 53
قَالُوا لَا تَوْجَلْ إِنَّا نُبَشِّرُكَ بِغُلَامٍ عَلِيمٍ
They said: "You don’t fear; indeed, we are giving you herald of a boy endowed with Knowledge".
It is the herald about son Ishaq as explained in verse 11: 71.