It was narrated from Asma' bint 'Umays that the Messenger of Allaah entered upon her one day and she had some spurge which she was grinding. He said: "What are you going to make with that?" She said: "We drink it." He said: "If anything were to ward off death or be of benefit against death, it would be senna."
Al-Haakim said: This Hadeeth has a Saheeh Isnaad, and Al-Dhahabi agreed with him. Mustadrak Al-Haakim, from the Hadeeth of 'Umar ibn Al-Khattab.
Dr. Muhammad 'Ali Al-Baar has written a paper on senna and its virtue according to the Sunnah, and he spoke a great deal about its medical benefits. Among other things he said:
Senna is regarded as a gentle stool softener and is not harmful. It works directly on the colon. It is an effective laxative and is a good medicine with no side effects, well balanced and dry. Its beneficial effects include working against depressing thoughts, cracks in the feet, tension in the muscles, the spread of hair, lice, scabies, pustules and itching. If it is cooked in olive oil and drunk, it expels putrid matter. It is also effective against pain in the back and hips. One of the features of senna is that it expels black bile and phlegm and strengthens the heart. It is also useful in the case of chronic headaches and epilepsy; it gets rid of haemorrhoids; it is useful in the case of constipation as a stool softener and laxative. There is hardly any stool softener or laxative in the pharmacy that does not contain senna. There is no doubt that senna is one of the best stool softeners available.
Al-Senna Wa'l-Sanoot by Dr. Muhammad 'Ali Al-Baar.
Taken from, The Jinn and Human Sickness - Remedies in the Light of the Qur'aan and Sunnah by Dr. Abu'l-Mundhir Khaleel ibn Ibraaheem Ameen