Hebrews 6:13-18

For example, there was God’s promise to Abraham. Since there was no one greater to swear by, God took an oath in his own name, saying: “I will certainly bless you, and I will multiply your descendants beyond number.” Then Abraham waited patiently, and he received what God had promised. Now when people take an oath, they call on someone greater than themselves to hold them to it. And without any question that oath is binding. God also bound himself with an oath, so that those who received the promise could be perfectly sure that he would never change his mind. So God has given both his promise and his oath. These two things are unchangeable because it is impossible for God to lie. Therefore, we who have fled to him for refuge can have great confidence as we hold to the hope that lies before us.