Question: Can one eat from a friends house without his permission ?

Answer: Know that the majority of the scholars see that it is permissible for one to eat from his friends house even without his permission if he knows that he doesn’t mind, and they quoted this ayah in Surat An-Nur as an evidence:

There is no restriction on the blind, nor any restriction on the lame, nor any restriction on the sick, nor on yourselves, if you eat from your houses, or the houses of your fathers, or the houses of your mothers, or the houses of your brothers, or the houses of your sisters, or the houses of your father’s brothers, or the houses of your father’s sisters, or the houses of your mother’s brothers, or the houses of your mother’s sisters, or (from that) whereof you hold keys, or (from the house) of a friend. No sin on you whether you eat together or apart. But when you enter the houses, greet one another with a greeting from Allah (i.e. say: As-Salamu ‘Alaikum – peace be on you) blessed and good. Thus Allah makes clear the Ayat (these Verses or your religious symbols and signs, etc.) to you that you may understand.

Ayah 61.