Is it halal for a mother to walk around the house in front of her children with just her undergarments? Even when her excuse is “I gave a birth to all of you I can wear whatever I want”. What is the daleel? Jazak Allahu Khayran

No, this is not allowed, and she should have haya (shyness and dignity) as well. And the Messenger (صلى الله عليه وسلم) did not make any exception when he mentioned that any man cannot look at the awrah of another man, and any woman cannot look at the awrah of another woman.