Notifying someone that the food is haraam

Question

There was a situation the other day, where an acquaintance of mine was going to eat a bagel that he very much liked. Unknown to him, was that the bagel's ingredients contained gelatin. I looked it up to make sure and then I notified him.

I remember, once in the past, in similar situation, someone once told me something along the lines of "I shouldn't have told him because it won't be sin for him to eat the haraam since he didn't know, and that is was very unobvious."

Did I do the right thing, or how correct was that particular someone from the past?

Answer 1

You did the correct thing. If you had not informed him about it, he would probably eat it again.

Cursed were those who disbelieved among the Children of Israel by the tongue of David and of Jesus, the son of Mary. That was because they disobeyed and [habitually] transgressed. They used not to prevent one another from wrongdoing that they did. How wretched was that which they were doing.

-- The Holy Quran (5:78-79)

Read this: http://islamqa.info/en/11403

Answer 2

Yes indeed, that was the right thing to do. When a Muslim sees a fellow Muslim doing something wrong (knowingly or not), it is one's duty to mention that, so that the other Muslim can avoid that.

In addition to the Quranic Aayah in there other answer, there is a Hadith (link and link) about this:

Al muminu mira'atul momin

A Momin is a mirror for a Momim.

If there is some mark etc. on your face, only you can tell that by looking at a mirror. Same way, a Momin is to another Momin.