John Gill Commentary Psalms 116:16

"O Jehovah, truly I am thy servant: I am thy servant, the son of thy handmaid; Thou hast loosed my bonds." — Psalms 116:16 (ASV)

O Lord, truly I [am] your servant, I [am] your servant
Not merely by creation, and as obliged by providential favours; but by the grace of God, which made him a willing one: and he was so, not nominally only, but in reality; not as those who say Lord, Lord, but do not the will of God; whereas he served the Lord cheerfully and willingly, in righteousness and true holiness: and this he repeats for the confirmation of it, and to show his heartiness in the Lord's service, and his zealous attachment to him; and which he mentions, not as though he thought his service meritorious of anything at the hand of God; but that his being in this character was an obligation upon him to serve the Lord, and him only, and might expect his protection in it;

[and] the son of your handmaid ;
his mother was also a servant of the Lord; and had trained him up in his infancy in the nurture and admonition of the Lord; so that he was inured to it early, and could not easily depart from it;

you have loosed my bonds ;
the bonds of affliction and death in which he was held; these were loosed, being delivered from them, (Psalms 116:3Psalms 116:8) ; and the bonds of sin, and Satan, and the law, in whose service he had been, which was no other than a bondage; but now was freed from the servitude and dominion of sin, from the captivity of Satan, and the bondage of the law; and therefore, though a servant, yet the Lord's free man.