Historical Rules · 8 March 2024
Rule 702.124i
Official source text from the 8 March 2024 Rules release
“Partner with [name]” represents two abilities. It means “You may designate two legendary creature cards as your commander rather than one if each has a ‘partner with [name]’ ability with the other’s name” and “When this permanent enters the battlefield, target player may search their library for a card named [name], reveal it, put it into their hand, then shuffle.”