What is the definitive age limit for applying the Hadd for sexual intercourse with a minor?

Primary text

The correct position holds that the Hadd is obligatory upon the legally responsible party (mukallaf) whenever penetration is physically possible for both parties involved. The determination of Hadd should not be restricted by the arbitrary ages of nine or ten years. Legal limitations (Tawqif) require specific religious text, which is absent here. The fact that sexual gratification is generally possible around age nine does not preclude it occurring before that age, just as puberty, generally occurring around fifteen, can occur earlier.