Sunan an-Nasa'i 993

It was narrated from Aishah that:The Messenger of Allah (ﷺ) sent a man on a campaign, and he used to recite to his companions when leading them in prayer, and would conclude with 'Say: He is Allah, (the) One.' When they returned, they told the Messenger of Allah (ﷺ) about that. He said: "Ask them why he did that." So they asked him and he said: "Because it is a description of the Most Merciful, the Mighty and Sublime, and I love to recite it." The Messenger of Allah (ﷺ) said: "Tell him that Allah (SWT), the Mighty and Sublime, loves him