Which by his strength setteth fast the mountains - Fixing them firm on their foundations. This is an exhibition of vast strength or power on the part of God, as if he fixed them so firm that they could not be moved - as if he handled with ease those vast masses of matter, with all their rocks and forests - and caused them to repose steadily and calmly on their foundations. We have few more exalted conceptions of the power of God than to suppose him lifting with ease a vast mountain; letting it down where he pleases, and settling it so firmly that it cannot be moved.
Being girded with power - That is, they seemed to be surrounded or encompassed with power, as a man girds himself up when he wishes to put forth a great effort of strength.