her-with', Hebrew ba-zo'th, bezo'th, "in," "by," or "with this" (Eze 16:29; Mal 3:10, "Prove me now herewith, saith Yahweh").
⇒See the definition of herewith in the KJV Dictionary
The Revised Version (British and American) has "herein" for "to do this" (Ezr 4:22); for "in these things" (Ro 14:18); "of them that have sinned heretofore" for "which have sinned already" (2Co 12:21); "hereunto" for "thereunto" (1Pe 3:9); "herewith" for "thus" (Le 16:3).
W. L. Walker