Danger of leaving Muslim child with a non-Muslim grandparent
2-1-2014 | IslamWeb
Question:
Assalaam alaikum, I am planning to move with my family to my parent's house for a few months to save money on rent. Alhamdulilaah my wife and I are firm in our eeman, but my mother is a Christian and does not have an understanding of tawheed and disagress with our aqidah. She prays, carries the cross, etc. We have a baby daughter, and if for example we left our daughter alone with her (like if we went shopping) and she said some Christian prayers over her or made the sign of the cross, etc., does this come under the ruling of magic or using jinn? If we don't move to their house, what about visiting them--is this permissible, as I don't know what Christian things she may do, either hidden/silently (like hidden prayers against our beliefs or requesting that we abandon our Islam, may Allaah protect us) or openly? Does this count as magic or using jinn against my family and I? wa alaikum assalaam
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad 
is His Slave and Messenger.
If your mother says some prayers or gestures to your daughter with the sign of the cross, then this does not necessarily mean that it is a kind of magic or using of jinn. You should not interpret the behavior of your mother as being magic or using jinn unless this is proven.
There is no doubt that leaving your daughter with her grandmother is dangerous for your daughter, as the falsehood she sees your mother doing may become imprinted in her memory and this may have bad effects on her in the future. It is for this reason that the majority of the jurists are of the view that the mother loses the child custody right if she is non-Muslim or dissolute.
However, moving to reside with your mother or visiting them is permissible but one should express disapproval of the falsehood in a gentle manner as we have previously clarified in Fatwa 90759. You should express disapproval of what is apparent and you should not investigate what she hides.
Allaah Knows best.