Charles Ellicott Commentary Numbers 24:6

"As valleys are they spread forth, As gardens by the river-side, As lign-aloes which Jehovah hath planted, As cedar-trees beside the waters." — Numbers 24:6 (ASV)

As gardens by the river’s side.— It is probable that the allusion may be to the Euphrates, although the definite article is not prefixed to the word nahar (river) in the Hebrew. (Compare to Isaiah 7:20.)

As cedar trees beside the waters. — The difference between cedars which grow beside running water which their roots can reach, and the ordinary type of cedars which throw out their strength in lateral branches is illustrated in Ezekiel 31:3-4, where the proud Assyrian is compared to a cedar having his top among the thick boughs (or, the clouds), which the waters made great. (Psalms 92:12.)