Riyad us Saliheen: Hadith 1290

I heard the Messenger of Allah (ﷺ) as saying, "Observing Ribat in the way of Allah for a day and a night is far better than observing Saum (fasting) for a whole month and standing in Salat (prayer) in all its nights. If a person dies (while performing this duty), he will go on receiving his reward for his meritorious deeds perpetually, and he will be saved from Al- Fattan."

[Muslim].