Wherefore watch ye for therefore watch, A.V.; remembering for and remember, A.V.; admonish for warn, A.V. By the space of three years ( τριετίαν). The word is only found here in the New Testament; but it is used in the LXX.
of Isaiah 15:5 and 2 Chronicles 31:16, and in classical Greek. We have here one of the few chronological data in the Acts. Three years includes the whole of his sojourn at Ephesus as his headquarters.
There were first the three months during which he preached in the synagogue; then the two years which he spent in preaching in the school of Tyrannus, and which terminated with the incident of burning the books of magic (Acts 19:8, Acts 19:10, Acts 19:19).
Then there was an indefinite time described in Acts 19:22 as "for a while" ( αὐτὸς ἐπέσχε χρόνον), during which he was busy making plans, probably writing letters, sending off Timothy and Erastus to Macedonia, and perhaps making missionary expeditions in the neighborhood.
This may have occupied three or four months longer, and made up a term of two years and six, seven, or eight months, which would quite justify the term τριετία. Every one. Each one separately, not merely the whole flock together.
A weighty lesson for every one who has the cure of souls (comp. John 10:3). Night and day. The night is mentioned first, in accordance with Hebrew usage (Genesis 1:5, Genesis 1:8, Genesis 1:13, etc.; comp.
the word νυχθήμερον in 2 Corinthians 11:25) St. Paul enforces the word "Watch," so appropriate to shepherds who watch over their flocks by night (Luke 2:8), by his own example of admonishing by night as well as day.