NET
21 Like charcoal is to burning coals, and wood to fire, so is a contentious person to kindle strife.
Darby
21 [As] coals for hot coals, and wood for fire, so is a contentious man to inflame strife.
KJV
21 [As] coals [are] to burning coals, and wood to fire; so [is] a contentious man to kindle strife.