سنن أبي داود

Narrated Ya'la b. Umayyah: I remarked to 'Umar al-Khattab: Have you seen the shortening of the prayer by the people today while Allah has said: "If you fear that those who are infidels may afflict you", whereas those days are gone now? He replied: I have wondered about the same matter for which you wondered. So I mentioned this to the Messenger of Allah (ﷺ). He said: It is an act of charity which Allah has done to you, so accept his charity.