had sworn

2 Samuel 21:7
Now the king spared Mephibosheth son of Jonathan, the son of Saul, because of the oath before the LORD between David and Jonathan son of Saul.

Psalm 15:4
who despises the vile but honors those who fear the LORD, who does not revise a costly oath,

Ecclesiastes 5:2, 6
Do not be hasty to speak, and do not let your heart be hasty to utter a word before God. After all, God is in heaven and you are on earth. So let your words be few. . . .

Ecclesiastes 9:2
It is the same for all: There is a common fate for the righteous and the wicked, for the good and the bad, for the clean and the unclean, for the one who sacrifices and the one who does not. As it is for the good, so it is for the sinner; as it is for the one who makes a vow, so it is for the one who refuses to take a vow.