Hebrews 6:16

James Moffatt - New Testament

For as men swear by a greater than themselves, and as an oath means to them a guarantee that ends any dispute,

Cross References

Hebrews 6:13

For in making a promise to Abraham God swore by himself (since he could swear by none greater),

Galatians 3:15

To take an illustration from human life, my brothers. Once a man's will is ratified, no one else annuls it or adds a codicil to it.