Shama-il Tirmidhi Chapter 046, Hadith Number 008 (320).

Anas Radiyallahu 'Anhu reports that Rasulullah Sallallahu 'Alayhi Wasallam said: "Even if I am given a foot of a goat as a present, I will accept it, and if I am invited to partake of it, I will surely accept that invitation".

Commentary
It does not even come to mind that why should I accept such an ordinary small article, or accept an invitation to partake of it. I think of it as a blessing of Allah and accept it whole heartedly. The actual reason for accepting an invitation is not the food but to encourage the host and keep one happy.