Arabic text
عَنْ عَبْدِ اللهِ بْنِ بُسْرٍ رضي الله عنه أَنَّ رَجُلاً قَالَ: يَا رَسُولَ اللهِ إِنَّ شَرَائِعَ الإِسْلاَمِ قَدْ كَثُرَتْ عَلَيَّ، فَأَخْبِرْنِي بِشَيْءٍ أَتَشَبَّثُ بِهِ، قَالَ: «لاَ يَزَالُ لِسَانُكَ رَطْبًا مِنْ ذِكْرِ اللَّهِ».
Translation
‘Abdullah ibn Busr (may Allah be pleased with him) reported that a man said: O Messenger of Allah, the legislations of Islam have become too much for me, so inform me of something to hold on to. He said: "Keep your tongue moist with the remembrance of Allah."
Explanation
A man complained to the Prophet (may Allah's peace and blessings be upon him) that the supererogatory acts of worship had become too much for him and that he could not perform them given his weakness. He, then, asked the Prophet (may Allah's peace and blessings be upon him) to guide him to an easy deed that would bring abundant rewards so he could adhere and hold on to it. He (may Allah's peace and blessings be upon him) advised him to keep his tongue moist and moving by remembering Allah Almighty recurrently at all times and in all states by glorifying and praising Him, seeking forgiveness from Him, supplicating Him, etc.
Source: HadeethEnc.com