it most likely meant those faithfully serving as ministers/preachers teaching within individual congregations of Christianity,
DJ: that understanding comes close to what wt taught in old light, about the "slave" being christians as a class, or when they acted as teachers. (while at the time maintaining an absolute monopoly on the pulpit)
I thought it was an encouragement to do all kinds of good deeds, not only "spiritually", as is of course in the order to do humanitarian works in the parable of the sheep and goats, allways, not just in the "end times" btw.