Great Tika to the Verse 2.3 of "Shree Bhagavad-Gita". "MatRDevo Bhava" means "Respect you Mother as God (Deva)". You can also check this explanation on Quora - "What does "pitru devo bhava" means in Sanskrit?"
And the following is the excerpt from Sanskrit-Hindi Edition of "Shree Bhagavad-Gita" by Shree Ramanuja-Sampradaya (LINK TO E-BOOK), as you can see "Shree Padma-Purana" is being cited:
