John Gill Commentary Esther 3:5

"And when Haman saw that Mordecai bowed not down, nor did him reverence, then was Haman full of wrath." — Esther 3:5 (ASV)

And when Haman saw that Mordecai bowed not, nor did him
reverence
For, after the information given him, he observed and watched him, to see whether he bowed and did him reverence or not:

then was Haman full of wrath ;
exceedingly displeased and angry; it was such a mortification to him he could not bear.