But may we swear an oath in God’s name if we do it reverently? 

Deuteronomy 6:13 – Fear the Lord your God, serve him only and take your oaths in his name.

Deuteronomy 10:20 – Fear the Lord your God and serve him. Hold fast to him and take your oaths in his name.

Jeremiah 4:1-2 – “If you, Israel, will return, then return to me,” declares the Lord.  “If you put your detestable idols out of my sight and no longer go astray, and if in a truthful, just and righteous way you swear, ‘As surely as the Lord lives,’ then the nations will invoke blessings by him and in him they will boast.”

Hebrews 6:16 – People swear by someone greater than themselves, and the oath confirms what is said and puts an end to all argument.

Genesis 21:24 – Abraham said, “I swear it.”

Joshua 9:15 – Then Joshua made a treaty of peace with them to let them live, and the leaders of the assembly ratified it by oath.

1 Kings 1:29-30 – The king then took an oath: “As surely as the Lord lives, who has delivered me out of every trouble, I will surely carry out this very day what I swore to you by the Lord, the God of Israel: Solomon your son shall be king after me, and he will sit on my throne in my place.”

Romans 1:9 – God, whom I serve in my spirit in preaching the gospel of his Son, is my witness how constantly I remember you

2 Corinthians 1:23 – I call God as my witness—and I stake my life on it—that it was in order to spare you that I did not return to Corinth.