This is one of those perennial questions, and it came up again the other day so I thought I would summarize the issues. For more detail, see my commentary (pages 170-173).
Paul urges Timothy to insist that an elder is above approach. What this means is laid out in the following verses, and one of the requirements is that he is “a man of one woman,” or, “a husband of one wife,” mias gunaikos andra. What does this mean?
1. Some hold that it means an elder must be married. But the force of the construction places its emphasis on “one” (because of its location at the beginning of the phrase), makes Timothy and Paul ineligible for eldership, and runs counter to Paul's preference for celibacy.