Genesis 49:3-4

3“Reuben, you are my firstborn; My might, the beginning of my strength and vigor, Preeminent in dignity and preeminent in power [that should have been your birthright].

4But unstable and reckless and boiling over like water [in sinful lust], you shall not excel or have the preeminence [of the firstborn], Because you went up to your father’s bed [with Bilhah]; You defiled it—he went up to my couch.