Fasting of children
Question: My young child insists on fasting (during) Ramadan despite it harming him due to his young age and weak health. So, can I use harshness with him to make him break his fast?
Answer: If he is young and has not attained puberty, then fasting is not incumbent upon him. However, if he is capable of fasting without hardship then he should be instructed to do so. The sahabah (may Allah be pleased with them) used to accustom their children to fasting, such that when a young one from amongst them would cry, they would distract him from his hunger by giving him a toy. However, if it is established that fasting is harming the child then he must be prevented from it; Just as Allah (Glory be to Him) has prohibited us (the parents) from giving money to them for fear of misuse, then certainly the fear of any harm upon them is more of a reason to prevent them from fasting. However, preventing them should not be through use of force and harshness, for certainly this is not befitting in bringing them up.
[Fatwas and messages of Shaykh Ibn `Uthaymeen: 493/1].