Abu Musa (May Allah bepleased with him) reported:
Messenger of Allah (ﷺ) said, "The relationship of the believer with another believer is like (the bricks of) a building, each strengthens the other." He (ﷺ) illustrated this by interlacing the fingers of both his hands.[Al-Bukhari and Muslim].
Arabic/English book reference: Book 1, Hadith 222