So Sistani (seen above) was asked about sex with a girl who is nine years old. He said: that "it is not permissible to enter the wife before she completes her nine-year old, whether intercourse was continuous or interrupted. As for the rest of enjoyments, like touching with desire or kissing or embracing or entering between legs, they are fine."
"مسألة 8: لا يجوز وطء الزوجة قبل إكمال تسع سنين، دواماً كان النكاح أو منقطعاً، واما سائر الاستمتاعات كاللمس بشهوة والتقبيل والضم والتفخيذ فلا بأس بها،" (thanks Sajjad)
PS You may find this in Kitab An-Nikah in Minhaj As-Salihin.
