Hebrews 6:13-16

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.