The Book of the Commencement of the Prayer
11/51. Chapter:
The Prostration in: "When the heaven is split asunder"
Sunan an-Nasai
أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى، قَالَ حَدَّثَنَا قُرَّةُ بْنُ خَالِدٍ، عَنْ مُحَمَّدِ بْنِ سِيرِينَ، عَنْ أَبِي هُرَيْرَةَ، قَالَ سَجَدَ أَبُو بَكْرٍ وَعُمَرُ - رضى الله عنهما - فِي { إِذَا السَّمَاءُ انْشَقَّتْ } وَمَنْ هُوَ خَيْرٌ مِنْهُمَا .
It was narrated that Abu Hurairah said: "Abu Bakr and Umar prostrated during: 'When the heaven is split asunder,' as did the one who was better than them (the Prophet (ﷺ)). "
Reference : Sunan an-Nasa'i 965In-book reference : Book 11, Hadith 90English translation : Vol. 2, Book 11, Hadith 966