In what situation for a righteous believer, is it best for Allah to take his soul?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The best condition in which the soul of the believer is taken is whenever he is doing a good deed or an act of worship. This will be a good end for him, since what matters is one’s final deeds. The Messenger of Allah said: “When Allah wills good for His slave, He sweetens him.” He was asked, “What is this sweetening?” He said, “Allah guides him to do a righteous deed before he dies, then He takes his soul whilst he is in that state.” [Narrated by Ahmad]

Also, it was narrated that Huthayfah said: “Whoever says Laa ilaaha illa-Allah (there is none worthy of worship except Allah), seeking the Countenance of Allah thereby, and that was the last of his deeds, will enter Paradise. Whoever fasts one day, seeking the Countenance of Allah thereby, and that was the last of his deeds, will enter Paradise. Whoever gives charity, seeking the Countenance of Allah thereby, and that was the last of his deeds, will enter Paradise.” [Narrated by Ahmad]

Allah Knows best.