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.