It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was walking in intense heat when the strap of his sandal (peace and blessings be upon him) broke, so a man brought a strap and fitted it into his sandal (peace and blessings be upon him). The Messenger of Allah (peace and blessings be upon him) said: "If only you knew what a great favour you have done for the Messenger of Allah (peace and blessings be upon him)! If only you knew what a great favour you have done for the Messenger of Allah (peace and blessings be upon him) (you would be amazed)!"
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7834