Sahih Muslim Book 20, Hadith Number 4676.

Chapter : Jihad not compulsory for those who have a genuine excuse.

It has been narrated on the authority of Abu Ishaq, that he heard Bara’ talking about the Qur’anic verse: “Those who sit (at home) from among the believers and those who go out for Jihad in the way of Allah are not equal” (iv. 95). (He said that) the Messenger of Allah (may peace be upon him) ordered Zaid (to write the verse). He brought a shoulder-blade (of a slaughtered camel) and inscribed it (the verse) thereon. The son of Umm Maktum complained of his blindness to the Holy Prophet (may peace be upon him). (At this) descended the revelation: “Those of the believers who sit (at home) without any trouble (illness, incapacity, disability)” (iv. 95). The tradition has been handed down through two other chains of transmitters.