It is narrated from Sayyiduna al-Irbad bin Sariyah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was asked about the slaughtered animals of the Christians and their festivals, and he (peace and blessings be upon him) said: "If you do not eat it, then feed it to me."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 15743