Al-Rubay’ bint Mu’awwidh (may Allah be pleased with her) said, speaking about Ramadan when it was made obligatory: “We used to make our children fast, and we would make them a toy made out of wool. If any one of them started to cry for food, we would give them that toy to play with until it was time to break the fast.” [al-Bukhari, Fath, no.1960]
Children should be instructed to fast at the age of seven, if they are able to, and may be pushed at the age of ten if he does not fast, just as in the case of salaah. (See al-Mughni, 3/90)
The child will be rewarded for fasting, and the parents will be rewarded for bringing him up properly and guiding him to do good.
Some people do not think it is important to tell their children to fast; indeed, a child may be enthusiastic about fasting and may be capable of doing it, but his father or mother may tell him not to fast, out of so-called “pity” for him.
They do not realize that true pity and compassion consist of making him get used to fasting.
Allah says (interpretation of the meaning): “O ye who believe! save yourselves and your families from a Fire whose fuel is Men and Stones, over which are (appointed) angels stern (and) severe, who flinch not (from executing) the Commands they receive from Allah, but do (precisely) what they are commanded.” [Surah Al Tahrim 66:6]
Extra attention must be paid to the matter of a girl’s fasting when she has just reached maturity, because she may fast when she has her period, out of shyness, and then not make up the fast later.