Charles Ellicott Commentary 1 Timothy 3:10

"And let these also first be proved; then let them serve as deacons, if they be blameless." — 1 Timothy 3:10 (ASV)

And let these also first be proved.—No formal investigation, either in public before the congregation, or in private before Timothy and his fellow presbyters, is referred to here. What is most probably the meaning of the word is that the deacon should, for a time, perform many of the various duties on probation to test his fitness before he was formally set apart for the holy office. So much of the work belonging to these officials of the early Church necessarily involved a partially secular character, that such a trial of their fitness could readily be made.

Then let them use the office of a deacon.—Better rendered, let them serve as deacons, if, after the trial, inquiry, and period of probation, they are found blameless.