In the name of Allah, the Beneficent, the Merciful
Islam does not allow sexual contact between children and adults. A man may only have sexual contact with a woman to whom he is married, and a marriage may not be consummated until she has become an adult.
وَلَا تَقْرَبُوا الزِّنَا إِنَّهُ كَانَ فَاحِشَةً وَسَاءَ سَبِيلًا
Do not approach unlawful sexual intercourse. Verily, it is immoral and an evil way.
Surat al-Isra’ 17:32
The jurists only discussed the issue of ‘thighing’ (mufakhadhah) in the context of marriage.
The Kuwaiti Encyclopedia of Fiqh states:
يَحْرُمُ عَلَى الرَّجُل مُفَاخَذَةُ الْمَرْأَةِ الأْجْنَبِيَّةِ
It is forbidden for a man to rub the thighs of an unrelated woman.
Source: Al-Mawsū’at al-Fiqhīyah al-Kuwaytīyah 32/56
أَمَّا مُفَاخَذَةُ غَيْرِ الزَّوْجَةِ مِنَ الْمَرْأَةِ الأْجْنَبِيَّةِ وَنَحْوِهَا فَحَرَامٌ
As for rubbing the thighs of an unrelated woman besides his wife and so on, it is forbidden.
Source: Al-Mawsū’at al-Fiqhīyah al-Kuwaytīyah 38/241
The jurists discussed this issue because it is relevant to the ritual validity of ablution, the fast of Ramadan, and the Hajj pilgrimage. For instance, they wanted to determine whether this type of sexual contact between spouses would invalidate the fast or not.
The general rule in regards to sexual intercourse is that it must not cause harm, and jurists recognized that sexual contact at a young age is harmful.
‘Ubadah ibn al-Samit reported: The Messenger of Allah, peace and blessings be upon him, issued a decree:
لاَ ضَرَرَ وَلاَ ضِرَارَ
Do not cause harm or return harm.
Source: Sunan Ibn Mājah 2340, Grade: Sahih
Al-Khatib al-Shirbini writes:
وَيَحْرُمُ وَطْءُ مَنْ لَا تَحْتَمِلُ الْوَطْءَ لِصِغَرٍ أَوْ جُنُونٍ أَوْ مَرَضٍ أَوْ هُزَالٍ أَوْ نَحْوِ ذَلِكَ لِتَضَرُّرِهَا بِهِ
Sexual intercourse is forbidden for any female who is incapable of intercourse, either due to young age, sickness, thinness, or likewise, as it would harm her.
Source: Mughnī al-Muḥtāj 4/373
The principle of no-harm applies not only to physical harm, but also to the psychological and emotional harm that is caused by unwanted or premature sexual contact.
In sum, there is no legal permission in Islam for sexual contact between children and adults.
Success comes from Allah, and Allah knows best.