Hadith 231

Bulugh al-Maram

Book 2: The Book of Prayer
Hadith 231
وَهِيَ فِي رِوَايَةٍ لَهُ : { وَلَمْ يَسْجُدْ حَتَّى يَقَّنَهُ اَللَّهُ تَعَالَى ذَلِكَ } .‏ 1‏
And in another narration:

"and he did not prostrate till Allah made him certain of this (i.e. as-Sahw)."