It was narrated that Abu Musa Al-Ash'ari said:
"The Messenger of Allah (ﷺ) said: 'The likeness of the heart is that of a feather blown about by the wind in the desert.'" (AR)
English reference (AR): Vol. 1, Book 1, Hadith 88 (AR)
Arabic reference (AR): Book 1, Hadith 93 (AR)