Bismillah hir Rahman ir Raheem
There is no doubt that from the affairs that every Muslim father and mother will be questioned about on the Day of Judgment will be the raising of one’s children. The Prophet (salAllahu wa salem) said:
“All of your are shepherds and all of you will be questioned concerning his flock.”
Due to this reality, we find that the Salaf were very diligent in raising their children (from young)upon righteousness.
Ibn Umar was reported to have said:
“Raise your children correctly, verily you are responsible for them and you will be questioned regarding your rearing of them.” (Shu’ab al Eman 8295)
Mu’awiyah ibn Qura is reported to have said to his children after praying Salatul ‘Isha:
“Oh my children, sleep (early), it’s possible that Allah will bless you by allowing you to stand a portion of the night in prayer.” (Zuhd by Imam Ahmed 234)
Saleh ibn Ahmed bin Hanbal is reported to have said:
“My father (Imam Ahmed) would call me whenever a righteous man visited him, in order for me to look at that man, in hopes that I would be like that person.” (Siyar 12/530)
If one were to look into the books of the people of knowledge he would find that the Salaf were also diligent with regards to the dress of their children. An example of this is in the following statements:
Jabir ibn Abdullah is reported to have said:
“We used to prevent our young boys from wearing silk, and we would allow it for our young girls” (Sahih Abi Dawud 3424)
Abdur Rahman bin Yazid said:
“I was in the company of Ibn Masoudwhen a young boy wearing silk approached, upon seeing him Ibn Masoud removed the silk from the boy and ripped it.” (Ibn Hazm in Muhalah 4/40)
Ibn Qudamah mentioned in Al Mugni:
“It is also forbidden for the parent to allow his/her child to wear that which is forbidden, just as it is prohibited to allow them to drink alcohol or indulge is usary.” (Al Mugni 1/344)
Ibn Taymiyyah mentioned:
“…that which is forbidden for the male to wear, it is likewise forbidden for him to allow his child to wear…” (Mejmoo’22/139)
Although the above statements are addressing the wearing of silk, these proofs along with their comments can also be applied to the wearing of the pants below the ankle, and Allah knows best.
Sheikh Muhammed bin Saleh al Uthaymeen (may Allah have mercy on him) said in responce to a question posed to him concerning the ruling on children’s clothing which contains pictures. The Sheikh responded: The people of knowledge have mentioned that it is forbidden to allow a child to wear that which is forbidden for a grown person to wear… (he continued to deal with the issue of pictures on clothing). Then the questioner replied: Does this ruling also apply to isbal for boys? They Sheikh said: Yes, it also applies to isbal for boys. (Important Questions for the Muslim Family pg.144)
Sheikh Abdullah Al Ghudayan (may Allah preserve him) said concerning Isbal for the young boys: The parents should condition their children to dress Islamically while they are still at a very young age. (Weekly gathering with the Westeners, Riyadh)
I hope and pray this brings some clarity.