Ya'la b. Umayya said

I remarked to ‘Umar b. al-Khattab that Allah had said, “You may shorten the prayer,” only “if you fear those who are infidels may afflict you” (Al-Qur’an; 4:101), whereas the people were now safe. He replied that he had wondered about the same matter, so he asked Allah's Messenger ﷺ and received the reply, “It is an act of charity which Allah has done to you, so accept His charity.” Muslim transmitted it.