Khalq Af'aal Al-'Baad by Al-Bukhari

“to unhonne kaha ki balki yeh hadees jo hai, yeh Prophet ke last stage ki hai, jab he was very sick and he was about to die. us waqt ki baat hai ki Hazrat Muaz ibn Jabal ne poochha ki "Which deed is the best and most beloved to Allah?" to RasoolAllah ne jawab diya, "That you die while your tongue is moist with the remembrance of Allah."”