Jamieson, Fausset and Brown on 1 Corinthians 4:19

19. Alford translates, "But come I will"; an emphatical negation of their supposition (1Co 4:18).

shortly--after Pentecost (1Co 16:8).

if the Lord will--a wise proviso (Jas 4:15). He does not seem to have been able to go as soon as he intended.

and will know--take cognizance of.

but the power--I care not for their high-sounding "speech," "but" what I desire to know is "their power," whether they be really powerful in the Spirit, or not. The predominant feature of Grecian character, a love for power of discourse, rather than that of godliness, showed itself at Corinth.