Reyav, maestro herrero

If a creature you control that's enchanted and equipped attacks, Reyav's ability will trigger only once for that creature. (Don't worry. Multiple instances of double strike are redundant. You're not missing much.)

The creature needs to be enchanted or equipped at the moment it's declared as an attacker to cause Reyav's ability to trigger. If the creature is no longer enchanted or equipped (or no longer attacking) as the ability tries to resolve, the ability still resolves.