Is it permissible for the husband to rub the clitoris (the small sensitive organ above the opening of the urethra, which is homologous to the penis) of his wife until she has sexual climax?
Yes it is permissible. One should note that all forms of sexual activities are permissible in general between husband and wife except those which are clearly marked as forbidden in Islam such as sexual intercourse during menstrual cycle etc...
And Allah knows best.
Mufti Ikram ul Haq
Fatwa Center of America