Parashat Mattot/Masei
Vows and oaths were traditionally stated with “As the LORD lives” or “I swear by the LORD”. So when someone did not keep their vow or oath, they were profaning the name of God.
God Himself also makes oaths. Just as people must keep their oaths and sanctify the name of God, so God must, and will keep what He has promised!
By Myself I have sworn; from my mouth has gone out in righteousness a word that shall not return: ‘To me every knee shall bow, every tongue shall swear allegiance.’
Isaiah 45:23