Sahih Muslim 1890
صحيح مسلم#1890SahihA'isha reported:The Messenger of Allah (ﷺ) sent a man in charge of an expedition and he would recite for his Companions during their prayer, ending (recitation) with:" Say, He is God, One." When they returned mention was made of it to the Messenger of Allah (ﷺ). He (the Holy Prophet) told them to ask him why he had done like that. So they asked him and he said: Verily, it is an attribute of the Compassionate One, and (for this reason) I love to recite it. The Messenger of Allah (ﷺ) thereupon said: Inform him that Allah loves him
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 6:318