Isaiah 49:15 Can a woman forget her sucking child, That she should not have compassion on the son of her womb? Yea, they may forget, Yet will I not forget thee.
A mother may forget her baby but God will never forget Israel. A mother may mistreat her baby but God will not do that to Israel.
In the New Testament we are given the same promises. He will take care of us. We can trust Him!