Numbers 21:17 - Matthew Poole's English Annotations on the Holy Bible

Israel sang this song, to praise God for giving them such a seasonable blessing, before they asked it, or complained for the want of it. Spring up; give forth thy waters that we may drink. Heb. Ascend, i.e. let thy waters, which now lie hid below in the earth, ascend for thy use. It is either a prediction that it should spring up, or a prayer that it might, or a command in the name of God directed to the well, by a usual prosopopaeia, as when God bids the heavens hear, and the earth give ear, Isaiah 1:2. Any of these ways it shows their faith. Sing ye unto it; or, sing ye of it; or, answer to it or concerning it; it being the manner of the Jewish singers that one should answer to another, of which see Exodus 15:21 1 Samuel 18:7.