Genesi 38:8

And Judah said unto Onan, Go in unto thy brother's wife, and marry her, and raise up seed to thy brother.

Ver. 8. And Judah said unto Onan.] At fourteen years of age likewise. For, from the birth of Judah to their going down to Egypt, were but forty-three years. And yet before that, Pharez had Hezron and Hamul, Gen 46:12 being married about the fourteenth year of his age; which was, doubtless, too soon. Childhood is counted and called the flower of age. 1Co 7:36 And so long the apostle would have marriage forborne.

While the flower of the plant sprouteth, the seed is green, unfit to be sown. Either it comes not up, or soon withereth. Too early marriages is one cause of our too short lives. Pursuit of sexual pleasure is death's best harbinger, saith one.