Sahih Muslim 145
Sahih Muslim · Book 1: The Book of Faith · Clarifying that Islam started as something strange, and will revert to being something strange, and it will retreat between the two Masajid
It is narrated on the authority of Abu Huraira that the Messenger of Allah (ﷺ) said:
حَدَّثَنَا مُحَمَّدُ بْنُ عَبَّادٍ ، وَابْنُ أَبِي عُمَرَ ، جَمِيعًا عَنْ مَرْوَانَ الْفَزَارِيِّ ، قَالَ ابْنُ عَبَّادٍ حَدَّثَنَا مَرْوَانُ، عَنْ يَزِيدَ، - يَعْنِي ابْنَ كَيْسَانَ - عَنْ أَبِي حَازِمٍ ، عَنْ أَبِي هُرَيْرَةَ ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " بَدَأَ الإِسْلاَمُ غَرِيبًا وَسَيَعُودُ كَمَا بَدَأَ غَرِيبًا فَطُوبَى لِلْغُرَبَاءِ " .
Islam initiated as something strange, and it would revert to its (old position) of being strange. so good tidings for the stranger.