Mesopotamian and Egyptian religion each independently developed a ceremony that opens or washes a divine image's mouth, and the resemblance in name has led to them being conflated in older popular writing, but Assyriologists and Egyptologists treat them as separate traditions with separate textual histories and different primary applications, the Egyptian rite centered on funerary images and mummies at burial, the Mesopotamian rite centered on the ongoing cultic life of temple statues.
The Mesopotamian ceremony is known mainly from two overlapping but not identical text traditions, one from Babylon and one from the Assyrian capital Nineveh, both preserved in first millennium copies though referencing older practice, and modern reconstruction, notably by the Assyriologists Christopher Walker and Michael Dick, has had to reconcile the two versions' differing sequences of incantations and ritual actions. The rite could also be repeated, since a damaged or repaired statue, or one that had been carried off as war booty and later recovered, required a fresh mis pi u pit pi before it could resume functioning as a living god's dwelling, which is one reason the ceremony recurs so often in the historical record of captured and returned cult images across Mesopotamian history.