Children are a trust that Allah (God) gives to parents as much as they are a precious gift. Parents are responsible for caring for and raising their children. Parents will be held accountable on judgment day for how they raised their children. A good upbringing must be accompanied by the teaching of Islam and an introduction to who Allah (God) is at an early age so that they can develop their Islamic worldview and virtues. A fun way to start introducing Allah (God) to your children is to read to them and encourage them to read.
