Shama-il Tirmidhi Chapter 46, Hadith Number 4 (316).
Anas Radiyallahu ‘Anhu reports: ”Rasulullah Sallallahu ‘Alayhi Wasallam accepted and attended invitations where bread made of barley, and stale fat a few days old was served (Without hesitation he accepted these invitations). Rasulullah Sallallahu ‘Alayhi Wasallam had pawned his armour to a Jew. Till the end of his life Rasulullah Sallallahu ‘Alayhi Wasallam did not possess a sufficient amount to release that armour'”.
When fat becomes stale it begins to smell. The serving of bread made of barley and stale fat could be ascertained from the status of the person or from experience, or even by the host himself saying this. Sayyidina Rasulullah Sallallahu ‘Alayhi Wasallam never made an excuse in accepting an invitation. The last sentence about the debt has been mentioned co-incidentally as it is part of the hadith. Some ‘ulama state that this is also a sign of humility. This was the reason of his poverty. Allah Ta’aala had given him the option of two things, if he wanted to become a Rasul with humbleness or become a Rasul with kingdom. Sayyidina Rasulullah Sallallhu ‘Alayhi Wasallam on his own accord chose the first one.