Why does “yaḥmilu” work without wāw in “The merchant arrived carrying his scale”?

Supplementary Practice 17: Market Inspection, Evidential Scope, and Rhetorical Precision

• It is jussive as a conditional answer
• It is a passive past verb
• It is an affirmative imperfect ḥāl with a pronominal link
• It is the predicate of inna