At the beginning of combat on your turn, put a charge counter on Gavel of the Righteous.
Equipped creature gets +1/+1 for each counter on Gavel of the Righteous.
As long as Gavel of the Righteous has four or more counters on it, equipped creature has
double strike (This creature deals both first-strike and regular combat damage.).
Equip — Pay
or remove a counter from Gavel of the Righteous
(Pay or remove a counter from Gavel of the Righteous: Attach to target creature you control. Equip only as a sorcery. This card enters the battlefield unattached and stays on the battlefield if the creature leaves.).