Charles Ellicott Commentary Psalms 119:42

"So shall I have an answer for him that reproacheth me; For I trust in thy word." — Psalms 119:42 (ASV)

VAU.

So shall I have. —Better literally, as the Septuagint and Vulgate, and I shall answer my reviler a word, for I trust in Thy word, i.e., when reproached it will be enough to pronounce God’s promise. The repetition of davar here and in Psalms 119:43 makes for this explanation in preference to that of the margin.