‘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)
Authentic hadithعن أنس بن مالك رضي الله عنه أَنَّ عَبْدَ الرَّحْمَنِ بْنَ عَوْفٍ، وَالزُّبَيْرَ بْنَ الْعَوَّامِ رضي الله عنهم ، شَكَوَا الْقَمْلَ إلَى رَسُولِ الله صلى الله عليه وسلم فِي غَزَاةٍ لَهُمَا فَرَخَّصَ لَهُمَا فِي قَمِيصِ الْحَرِيرِ وَرَأَيْته عَلَيْهِمَا.
Anas ibn Mālik (may Allah be pleased with him) reported: ‘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) during one of the battles, and so he granted them a concession to wear a silk shirt, and I saw them wearing that.
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.
Source · Narrated by Bukhari & Muslim
From the Hadith Encyclopedia (hadeethenc.com).