Historical Rules · 24 September 2021
Rule 702.145b
Official source text from the 24 September 2021 Rules release
Daybound is found on the front faces of some transforming double-faced cards and represents three static abilities. “Daybound” means “If it is night, this permanent enters the battlefield transformed,” “As it becomes night, if this permanent is front face up, transform it,” and “This permanent can’t be transformed except by its daybound ability.” See rule 724, “Day and Night.”