‘Abdur-Rahmān ibn ‘Awf and Az-Zubayr ibn al-‘Awwām (may Allah be pleased with both of them) complained of lice to the Messenger of Allah (may Allah's peace and blessings be upon him)

Explanation

A religion of ease, Islam gives concession in certain cases of need, i.e. allowing what is unlawful for a valid reason. The Prophet (may Allah's peace and blessings be upon him) allowed Az-Zubayr and ‘Abdur-Rahmān to wear a silk shirt since it wards off lice by what Allah has naturally created in it; likewise, it is a cure for itching. This concession is for these cases and the like.