KJV Genesis 35 : 22
And it came to pass, when Israel dwelt in that land, that Reuben went and lay with Bilhah his father’s concubine: and Israel heard it. Now the sons of Jacob were twelve:
Having heard what his elder son had done it seems Jacob kept quiet about the whole debacle
Interesting in the previous chapter to this incident his other two sons had also also committed a grievous act by killing the men of shechem and Jacob had rebuked them immediately there after
KJV Genesis 34 : 30
And Jacob said to Simeon and Levi, Ye have troubled me to make me to stink among the inhabitants of the land, among the Canaanites and the Perizzites: and I being few in number, they shall gather themselves together against me, and slay me; and I shall be destroyed, I and my house.
After having waited for some twenty seven years and on his deathbed Jacob finally pronounces his curse on Rueben
KJV Genesis 49 : 3 - 4
Reuben, thou art my firstborn, my might, and the beginning of my strength, the excellency of dignity, and the excellency of power: 4 Unstable as water, thou shalt not excel; because thou wentest up to thy father's bed; then defiledst thou it: he went up to my couch.
Why did Jacob have to wait this long before rebuking his son Reuben?