Commentaries:
Barnes' Notes
Once have I sworn by my holiness - That is, once for all; - a single oath - an oath once taken by me - makes it certain. To swear by his "holiness" is to pledge his own holy nature; to make it as certain as that he is holy; to stake the whole question of his holiness on that. That is, If this should not be accomplished - if he should fail in this - it would Proverbs that he was not a holy God.
That I will not lie unto David - Margin, as in Hebrew, "if I lie." The meaning is, He would be found faithful to the promise. See Psalms 89:3-4; compare II Samuel 7:8-16.
DISCLAIMER: Church of the Great God (CGG) provides these resources to aid the individual in studying the Bible. However, it is up to the individual to "prove all things, and hold fast to that which is good" (I Thessalonians 5:21). The content of these resources does not necessarily reflect the views of CGG. They are provided for information purposes only.