He bindeth up the waters in his thick clouds; i.e. he makes the clouds, that we see floating in the atmosphere, contain and hold the waters on which the productiveness of the earth depends, and which he restrains, or allows to fall in fertilizing rain, at his pleasure.
And the cloud is not rent under them. The metaphor is, no doubt, drawn from those water-skins, so well known in the East, and especially in Arabia, in which men stored the water for their journeys and other needs, which were liable to be "rent" by the weight of the liquid within them.