Illustrations paragraph 3

3. Know also that one must be very careful not to advise a person to make a partnership with someone if he knows some harm might come from it — for example, if the partner is poor, or not an honest person. The same applies to a shidduch (marriage match), or to a worker that people ask him about.

The whole ban of rechilus is about going and causing harm to the person spoken about. But the opposite — causing harm to Reuven by advising him to make a partnership with Shimon, or to make a match with him, when he knows that if it were about himself he would stay away from these people — is completely forbidden. It is included in "Do not put a stumbling block before the blind," which Chazal explained as "not to give him advice that is not fitting."

Some people stumble in this because of their own personal interests. It is a serious sin, because the desire for money leads them to break a Torah prohibition.