It was narrated from Abu Hurairah (RA) that the Messenger of Allah (peace be upon him) said: "Were it not that I would impose too ...
It was narrated from Abu Hurairah (RA) that the Messenger of Allah (peace be upon him) said: "Were it not that I would impose too much difficulty on my Ummah, I would have commanded them to delay 'Isha' and to use the Siwak for every prayer."
(Sunan an-Nasa'i, Book 6, Hadith 539)
source:HadithOfTheDay.com