Praise be to Allaah.

It was narrated from Abu Hurayrah that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “When any one of you enters upon his Muslim brother and he offers him food, let him eat from his food and not ask about it. And if he offers him something to drink, let him drink what he offers and not ask about it.” 

(Narrated by Ahmad, 8933. This hadeeth was classed as saheeh by al-Albaani in al-Silsilah al-Saheehah, 627). 

Shaykh al-Albaani said: 

The apparent meaning is that this hadeeth is to be interpreted as referring to a case where a person thinks it most likely that his Muslim brother’s wealth is halaal and that he avoids forbidden things. Otherwise it is permissible, indeed obligatory, to ask, as in the case of some Muslims who have settled in kaafir countries. In their case and in similar cases, we have to ask them about their meat, for example whether it is killed (by non-halaal methods) or slaughtered (according to sharee’ah). 

Al-Silsilah al-Saheehah, hadeeth 627.