Avicenna, Canon of Medicine: “This form of ablution is only beneficial if all the proper rules are observed, and if the age of the person, his physique and build,-; are suitable, and the season is appropriate (i.e. the summer). The contra-indications are: nausea, or a feeling of satiety associated with indigestion; vomiting; or diarrhoea; or want of sleep; or nasal catarrh. The person must not be at the age of boyhood, nor at old age. [Therefore he must be in the prime of life.] The moment chosen for the ablution should be one at which the body is light and the movements appropriate."
http://data.nur.nu/Kutub/English/Avicenna_Canon-of-Medicine_text.pdf