Albert Barnes Commentary Acts 20:29

"I know that after my departing grievous wolves shall enter in among you, not sparing the flock;" — Acts 20:29 (ASV)

For I know this. By what he had seen in other places; by his knowledge of human nature, and of the dangers to which they were exposed; and by the guidance of inspiration.

After my departing. His presence had been the means of guarding the church, and preserving it from these dangers. Now that the founder and guide of the church was to be removed, they would be exposed to dissensions and dangers.

Grievous wolves. Heavy, bareiv, strong, mighty, dangerous wolves—so strong that the feeble flock would not be able to resist them. The term wolves is used to denote the enemies of the flock—false, and hypocritical, and dangerous teachers. Compare to Matthew 10:16; See Barnes "Acts 7:15".

Enter in among you. From abroad; doubtless referring particularly to the Jews, who might be expected to distract and divide them.

Not sparing the flock. Seeking to destroy the church. The Jews would regard it with peculiar hostility, and would seek to destroy it in every way. Probably they would approach them with great professed friendship for them, and expressing a desire only to defend the laws of Moses.