Rashi on Isaiah
Ho! All who thirst Heb. הוֹי. This word הוֹי is an expression of calling, inviting, and gathering, and there are many in Scripture, [e.g.,] (Zech. 2:10) “Ho! Ho! and flee from the north land.”
Ibn Ezra on Isaiah
הוי Ho ! It is the sign of the vocative. Ho, every one that thirsteth, etc. With these words the Lord will address those who will then be desirous to accept the Law.