Genesis 49:3
Reuben, you are my firstborn, my might, and the beginning of my strength, the excellency of dignity, and the excellency of power:
Torrey's Topical Textbook—AKJV

Deuteronomy 21:17
But he shall acknowledge the son of the hated for the firstborn, by giving him a double portion of all that he has: for he is the beginning of his strength; the right of the firstborn is his.
Torrey's Topical Textbook—AKJV