سنن أبي داود

Narrated Abdullah ibn Abbas:

The Prophet (ﷺ) said: Do not cover the walls. He who sees the letter of his brother without his permission, sees Hell-fire.

Supplicate Allah with the palms of your hands; do not supplicate Him with their backs upwards. When you finish supplication, wipe your faces with them.

Abu Dawud said: This tradition has been transmitted through a different chains by Muhammad b. Ka'b; all of them are weak. The chain I have narrated is best of them; but it is also weak.