1253An NasaiSahih (Darussalam)أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ مِسْعَرٍ، عَنِ الْحَكَمِ، عَنْ أَبِي وَائِلٍ، عَنْ عَبْدِ اللَّهِ، قَالَ مَنْ شَكَّ أَوْ أَوْهَمَ فَلْيَتَحَرَّ الصَّوَابَ ثُمَّ لْيَسْجُدْ سَجْدَتَيْنِ .It was narrated that 'Abdullah said:"Whoever has doubt, or is not sure, let him estimate what is correct, then let him prostrate twice."Reference: Sunan an-Nasa'i 1246 In-book : Book 13, Hadith 68 English translation : Vol. 2, Book 13, Hadith 1247