He brought streams also out of the rock - literally, "flowings." The waters were poured out in an over-flowing stream. Those streams continued to flow, thus constituting a continued proof of the presence of God. See this fully explained in the notes at 1-Corinthians 10:4.

He brought streams also out of the rock,.... Which is expressed in the singular number, as also in Psalm 78:20, because the children of Israel were not come to Kadesh, and the second rock was not smitten when they lusted after flesh, and murmured against God, and tempted him, as is after related:
and caused waters to run down like rivers; from the descent of the rock, which followed them all the way in the wilderness; this was a most marvellous thing, that water should flow from a flinty rock upon striking it, from whence fire rather than water might have been expected; and that it should flow in such great abundance, and that from a rock in a wilderness.

Streams - Which miraculously followed them in all their travels, even to the borders of Canaan.