Charles H. Spurgeon on Psalms 81:10

I will fill it. Consider the import of the promise: Open thy mouth wide, and I will fill it. "Ask, and ye shall receive; seek, and ye shall find." Particularly,

1. If we open our mouths to God in prayer, he will fill them more and more with suitable petitions and arguments. When we attempt to open the mouth, God will open it still wider. Thus he dealt with Abraham when he interceded for Sodom; the longer he prayed, the more submissive and yet the more importunate he became. By praying we increase our ability to pray, and find a greater facility in the duty. "To him that hath shall be given, and he shall have more abundantly."

2. God will fill the mouth with abundant thanksgivings. Many of David's psalms begin with prayer, and end with the most animated praises. No mercies so dispose to thankfulness as those which are received in answer to prayer; for according to the degree of desire will be the sweetness of fruition...

3. We shall be filled with those blessings we pray for, if they are calculated to promote our real good and the glory of God. Do we desire fresh communications of grace, and manifestations of divine love; a renewed sense of pardoning mercy, and an application of the blood of Christ? Do we want holiness, peace, and assurance? Do we want to hear from God, to see him, and be like him? The promise is, My God shall supply all your need according to his riches in glory by Christ Jesus, Php 4:19. You shall have what you desire, and be satisfied: it shall be enough, and you shall think it so. "The Lord will give grace and glory: no good thing will he withhold from them that walk uprightly." Benjamin Beddome.