A.T. Robertson Commentary Acts 9:16

"for I will show him how many things he must suffer for my name`s sake." — Acts 9:16 (ASV)

I will shew (υποδειξω). Beforehand as a warning as in Lu 3:7 and from time to time.

He must suffer (δε αυτον παθειν). Constative aorist active infinitive (παθειν, from πασχω) covering the whole career of Saul. Suffering is one element in the call that Saul receives. He will learn "how many things" (οσα) are included in this list by degrees and by experience. A glance at 2Colossians 10-12 will show one the fulfilment of this prophecy. But it was the "gift" of Christ to Paul to go on suffering (πασχειν, present infinitive, Php 1:39).