Historical Rules · 20 November 2020
Rule 711.14
Official source text from the 20 November 2020 Rules release
When a transforming double-faced permanent transforms, it doesn’t become a new object. Any effects that applied to that permanent will continue to apply to it after it transforms. Example: An effect gives Village Ironsmith (the front face of a transforming double-faced card) +2/+2 until end of turn and then Village Ironsmith transforms into Ironfang. Ironfang will continue to get +2/+2 until end of turn.