Historical Rules · 25 September 2020
Rule 301.5c
Official source text from the 25 September 2020 Rules release
An Equipment that’s also a creature can’t equip a creature. An Equipment that loses the subtype “Equipment” can’t equip a creature. An Equipment can’t equip itself. An Equipment that equips an illegal or nonexistent permanent becomes unattached from that permanent but remains on the battlefield. (This is a state-based action. See rule 704.) An Equipment can’t equip more than one creature. If a spell or ability would cause an Equipment to equip more than one creature, the Equipment’s controller chooses which creature it equips.