Sunan Ibn Majah, Chapter: The Chapters of Establishing the Prayer and the Sunnah Regarding Them

"I asked Umar bin Khattab: 'Allah says: "And when you travel in the land, there is no sin on you if you shorten the prayer if you fear that the disbelievers may put you in trial (attack you), verily, the disbelievers are ever to you open enemies," [4:101] but now there is security and people are safe.' He said: 'I found it strange just as you do, so I asked the Messenger of Allah (saw) about that, and he said: "It is charity that Allah has bestowed upon you, so accept His charity." Daif