Albert Barnes Commentary Psalms 119:108

"Accept, I beseech thee, the freewill-offerings of my mouth, O Jehovah, And teach me thine ordinances." — Psalms 119:108 (ASV)

Accept, I beseech you, the free-will offerings of my mouth - Or, the meaning of the word here rendered "free-will," see the notes at Psalm 110:3. It conveys the idea that there is no constraint or compulsion; that the offering is a prompting of the heart.

The offering might be that of flour, or grain, or fruits, or property of any kind, as devoted to God; or it might be, as here, an offering of the lips, expressed in prayer and praise. Either of them might be acceptable to God; their acceptance in either case would depend on the good pleasure of God, and hence, the psalmist prays that his offering might be thus acceptable. Compare to Hebrews 13:15.

And teach me your judgments - Your commands; your laws. See the notes at Psalm 119:12.