ואכלת ושבעת וברכת

Yankele’s  Bo Bayom Bar Mitzva was on a Friday. His parents made a special Seudah for his

classmates  on Thursday  evening.  They finished with the meal 10 minutes after shkia

and  bentched  before Tzeis Hakochavim (night).

Does Yankele have to repeat the bentching again after  Tzeis Hakochavim ?  (within 72 minutes

 after finishing the meal )

R.Akivah Eiger (Haghaos R.A.E. Shulchan Aruch O. Ch. 184 :2  ) asks, what creates  the Chiyuv

 of Bentching , is it  the Achila & Sevia  or maybe only the Sevia is the mechayev and not the Achila*.

Yankele, ate while he was  a Koton, but was still  satisfied (full) when he became a Godol.(within 72 minutes)

If you need both Achila & Sevia then Yankele doesn’t need to repeat the Bentching.

(there was no achila as a godol)

If all you need is Sevia , then Yankele would be required to Bentch again. When he Benched

The first time he was a Koton  and wasn’t mechuyav to bentch. Now that he is a Godol  and is

still satisfied, he is required to Bentch again  Mideorysa .

*The Torah saidואכלת   to teach, that you need a מעשה אכילה   for the  Sevia.

(If  fed with a feeding tube, bentching is not  required.) and not that

the achila is the mechayav.