Gill Commentary:
The husband of one wife; which is not to be understood in a mystical and allegorical sense of his being the pastor of one church, since the apostle afterwards speaks of his house and children, that are to be ruled and kept in good order by him, in distinction from the church of God; but in a literal sense of his conjugal estate; though this rule does not make it necessary that he should have a wife; or that he should not marry, or not have married a second wife, after the death of the first; only if he marries or is married, that he should have but one wife at a time; so that this rule excludes all such persons from being elders, or pastors, or overseers of churches, that were "polygamists"; who had more wives than one at a time, or had divorced their wives, and not for adultery, and had married others. Now polygamy and divorces had very much obtained among the Jews; nor could the believing Jews be easily and at once brought off of them. And though they were not lawful nor to be allowed of in any; yet they were especially unbecoming and scandalous in officers of churches. So the high priest among the Jews, even when polygamy was in use, might not marry, or have two wives, at once; if he did, he could not minister in his office until he divorced one of them (u). For it is written, Lev_21:13, "he shall take a wife", אחת ולא שתים, "one, and not two" (w). And the same that is said of the high priest, is said of all other priests; see Eze_44:22, likewise the Egyptian priests might not marry more wives than one, though others might have as many as they pleased (x): and so the Flamines among the Romans (y). An elder or pastor must also be one that is
... or dead - you sure you'd want them all standing behind you?