Adam Clarke's Commentary on the Bible

Verse 14 (1 John 5:14)

This is the confidence - Παρῥησια , The liberty of access and speech, that if we ask any thing according to his will, that is, which he has promised in his word. His word is a revelation of his will, in the things which concern the salvation of man. All that God has promised we are justified in expecting; and what he has promised, and we expect, we should pray for. Prayer is the language of the children of God. He who is begotten of God speaks this language. He calls God Abba, Father, in the true spirit of supplication. Prayer is the language of dependence on God; where the soul is dumb, there is neither life, love, nor faith. Faith and prayer are not boldly to advance claims upon God; we must take heed that what we ask and believe for is agreeable to the revealed will of God. What we find promised, that we may plead.

- Adam Clarke's Commentary on the Bible