AVOUCH

a-vouch': In English Versions of the Bible only in Deuteronomy 26:17-18, in the sense of "to confess," "avow," "publicly and solemnly declare." The Hebrew form is likewise unique (Hiph. of 'amar).

From the International Standard Bible Encyclopedia
Edited by James Orr, published in 1939 by Wm. B. Eerdmans Publishing Co.