This verse is often misinterpreted as a blanket prosperity promise guaranteeing material abundance or unlimited worldly success to anyone who simply asks or claims it in faith, detached from its covenantal context of obedience and exclusive worship of Yahweh; surrounding verses reveal God's lament over Israel's unfaithfulness, showing that such fillings come only to those who heed His voice and reject foreign gods, not as a formula for selfish gain.
Psalms 81:10
King James Version (1769)
10 I am the Lord thy God, which brought thee out of the land of Egypt: open thy mouth wide, and I will fill it.
Psalms 81:10 conveys God's self-identification as the deliverer of Israel from Egyptian bondage, issuing a call to 'open thy mouth wide' as a metaphor for wholehearted trust and dependence on Him alone for provision, satisfaction, and every need, contrasting with Israel's tendency toward idolatry and self-reliance, and underscoring the blessings that flow from exclusive devotion within the covenant relationship.