Ayesha reported,
The Prophet ﷺ sent a man in command of a military expedition. This man used to lead his companions in prayer, and he would always conclude his recitation with "Say, He is Allah, the One" [Ikhlas 112:1]. When they returned, they mentioned this to the Prophet ﷺ.He said, "Ask him why he does that."So they asked him, and he replied, "Because it describes the Most Merciful, and I love to recite it."The Prophet ﷺ said, "Tell him that Allah loves him."
Azami 246
Sahihعن عائشة
أن النبي ﷺ بعث رجلا على سرية، وكان يقرأ لأصحابه به في صلاته فيختم ب {قل هو الله أحد} فلما رجعوا ذكروا ذلك للنبي ﷺ فقال: سلوه لأي شيء يصنع ذلك؟ فسألوه فقال: لأنها صفة الرحمن، وأنا أحب أن أقرأ بها. فقال النبي ﷺ: أخبروه أن الله يحبه.
Bukhari narrated it in the Book of Monotheism (7375), and Muslim in the Book of the Merits of the Quran (813), both from the hadith of Abdullah bin Wahb, who said, Amr bin Harith narrated to us, from Saeed bin Abu Hilal, that Abu Rijal Muhammad bin Abdul-Rahman narrated to him, from his mother Amra bint Abdul-Rahman, who had been raised in the household of Ayesha, from Ayesha, and she mentioned the same.