Jamieson, Fausset and Brown on 1 Corinthians 4:15

15. ten thousand--implying that the Corinthians had more of them than was desirable.

instructors--tutors who had the care of rearing, but had not the rights, or peculiar affection, of the father, who alone had begotten them spiritually.

in Christ--Paul admits that these "instructors" were not mere legalists, but evangelical teachers. He uses, however, a stronger phrase of himself in begetting them spiritually, "In Christ Jesus," implying both the Saviour's office and person. As Paul was the means of spiritually regenerating them, and yet "baptized none of them save Crispus, Gaius, and the household of Stephanas," regeneration cannot be inseparably in and by baptism (1Co 1:14-17).