have respect to him, etc. - though ye know not who he is, when perhaps he may be a heathen. It was the office of the deacons to direct to a seat the members of the congregation [Clement of Rome, Apostolical Constitutions, 2.57, 58].
unto him - not in the best manuscripts. Thus “thou” becomes more demonstratively emphatic.
there - at a distance from where the good seats are.
here - near the speaker.
under my footstool - not literally so; but on the ground, down by my footstool. The poor man must either stand, or if he sits, sit in a degrading position. The speaker has a footstool as well as a good seat.