Arabic text
عَنْ عَبْدِ اللَّهِ بْنِ بُسْرٍ رَضِيَ اللَّهِ عَنْهُ قَالَ: أَتَى النَّبِيَّ رَجُلٌ، فَقَالَ: يَا رَسُولَ اللَّهِ! إِنَّ شَرَائِعَ الإِسْلَامِ قَدْ كَثُرَتْ عَلَيْنَا، فَبَابٌ نَتَمَسَّكُ بِهِ جَامِعٌ؟ قَالَ: «لاَ يَزَالُ لِسَانُكَ رَطْبًا مِنْ ذِكْرِ اللَّهِ». وفي رواية: مِنْ حَدِيثِ مُعَاذِ بْنِ جَبَلٍ رَضِيَ اللَّهُ عَنْهُ: آخِرُ مَا فَارَقْتُ عَلَيْهِ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَنْ قُلْتُ: أَيُّ الأَعْمَالِ خَيْرٌ وَأَقْرَبُ إِلَى اللَّهِ؟ قَالَ: «أَنْ تَمُوتَ وَلِسَانُكَ رَطْبٌ مِنْ ذِكْرِ اللَّهِ عَزَّ وَجَلَّ».
Translation
‘Abdullah ibn Busr (may Allah be pleased with him) reported: A man came to the Prophet (ﷺ) and said: O Messenger of Allah, indeed, the laws of Islam are too many for us, so give us something comprehensive that we can hold on to. He said: "Keep your tongue moist with the remembrance of Allah." Another version reads: From the Hadīth of Mu‘ādh ibn Jabal (may Allah be pleased with him): The last thing upon which I parted from the Messenger of Allah (ﷺ) was that I asked: Which deeds are best and closest to Allah? He said: "That you die while your tongue is moist with the remembrance of Allah, the Exalted and Majestic."
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