John Gill Commentary Numbers 5:26

"and the priest shall take a handful of the meal-offering, as the memorial thereof, and burn it upon the altar, and afterward shall make the woman drink the water." — Numbers 5:26 (ASV)

And the priest shall take an handful of the offering, [even]
the memorial thereof
For good or evil, according as her works were, as Aben Ezra observes; a memorial for good, if innocent, and a memorial for evil, if guilty:

and burn [it] upon the altar ;
as the handful of other meat offerings used to be, (Leviticus 1:2) ;

and afterwards shall cause the woman to drink the water ;
oblige her to it; having proceeded thus far, and no confession made, namely, an oath taken, the curses of it written in a scroll and scraped into the waters, and the jealousy offering waved and offered.