Ya'la bin Umayyah (may Allah be pleased with him) said: I said to Sayyiduna Umar (may Allah be pleased with him): People still shorten the prayer today, whereas Allah's words are: "if you fear that those who disbelieve may put you to trial" [Surah al-Nisa: 101]. The fear has now gone. He said: I too wondered at what you wonder at. I mentioned this to the Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: "It is a charity that Allah has bestowed upon you, so accept Allah's charity."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5379