Charles Ellicott Commentary Acts 20:31

"Wherefore watch ye, remembering that by the space of three years I ceased not to admonish every one night and day with tears." — Acts 20:31 (ASV)

Therefore watch . . .—The word was, so to speak, an echo from our Lord’s teaching (Matthew 24:42; Matthew 25:13, and other passages), which could hardly have been unknown to St. Paul. Here, however, it receives a fresh significance from its connection with the term episcopi. Those who were the bishops, the overseers, the watchers of the flock, ought, above all others, to set an example of vigilance.

By the space of three years.—Strictly speaking, the narrative of the Acts accounts for three months’ preaching in the synagogue (Acts 19:8), two years in the school of Tyrannus (Acts 19:10), and an undefined period embracing the time immediately before and after the tumult of Demetrius. This would be enough to warrant him describing the time of his ministry, speaking roughly, as extending over three years.

To warn every one night and day with tears.—Compare Note on Acts 20:19.