Sunan an-Nasa'i 5034
It was narrated that Abu Hurairah said:
"The Messenger of Allah said: 'Indeed, this religion is easy, and no one will ever overburden himself in religion, except that it will overcome him. So seek what is appropriate, and come as close as you can, and receive the glad tidings (that you will be rewarded), and take it easy; and gain strength by worshipping in the mornings, afternoons, and during the last hours of the nights.'"
أَخْبَرَنَا أَبُو بَكْرِ بْنُ نَافِعٍ قَالَ حَدَّثَنَا عُمَرُ بْنُ عَلِيٍّ عَنْ مَعْنِ بْنِ مُحَمَّدٍ عَنْ سَعِيدٍ عَنْ أَبِي هُرَيْرَةَ قَالَ  قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِنَّ هَذَا الدِّينَ يُسْرٌ وَلَنْ يُشَادَّ الدِّينَ أَحَدٌ إِلَّا غَلَبَهُ فَسَدِّدُوا وَقَارِبُوا وَأَبْشِرُوا وَيَسِّرُوا وَاسْتَعِينُوا بِالْغَدْوَةِ وَالرَّوْحَةِ وَشَيْءٍ مِنْ الدَّلْجَةِ