On a very basic level, these men had to ensure that all the widows in the church community were provided for. Their fundamental duty then was to alleviate the needs of the poor, to serve the poor on behalf of Christ. This did not mean they had to do everything themselves (after all, there were only seven of them), but they had to make sure that the poor were being cared for. Additionally, there was another responsibility that is implicit to this work. Given the fact that there was grumbling amongst the Greek-speaking Christians, one can also see their task as one of encouraging fellowship and promoting unity between believers from different cultural or ethnic backgrounds.
3 Therefore, brothers, pick out from among you seven men of good repute, full of the Spirit and of wisdom, whom we will appoint to this duty.