For a statement to be excluded from the realm of rechilus and be classified instead as constructive, several conditions are necessary.
Condition #1: Fact of Hearsay
Most important is that one ascertain that the information is fully accurate. This involves both verification of the facts as well as a clear understanding of the situation (as was discussed regarding conveying negative information for a constructive purpose).
The commandment, “Do not stand aside while your fellow’s blood is being shed” (Vayikra19:16), obligates us to report constructive information if our knowledge of it is firsthand. Should one choose to speak of an alleged occurrence that he did not personally witness in order to save his fellow Jew from possible harm, it must be clearly stated that the information is based on hearsay and is not to be accepted as fact.
Condition #2: Thorough Understanding
Even when one has personally witnessed a situation, he must avoid hastily concluding that one party has harmed, or is about to harm, another. Often, it is impossible to fully understand the attitude and behavior of one person towards another without a thorough knowledge of their relationship until this point. What appears to be a sinister plot might actually be a plan of self-defense. Exposing the “plotter” in such a case might leave the real victim vulnerable and defenseless.
Condition #3: Reprove First
We have seen that with regard to loshon hora, one may not speak negatively about someone for a constructive purpose without first discussing the matter with that person. An exception to this rule is a case where speaking to the person could prevent the desired result from being achieved (See Days 45, 72).
With regard to rechilus, the exception may be more common than the rule. When an individual has already harmed someone or is about to harm someone, one should not enter into a discussion with him concerning the matter if this could make it more difficult for the victim to protect himself or attain restitution.
In other situations of rechilus, tochachah (rebuke) toward the perpetrator is a prerequisite for relating rechilus for a constructive purpose. A discussion with the person could preclude the need to speak rechilus concerning him, and dispel suspicions regarding the speaker’s true intentions (Rebuke is further discussed in Days 152-153).
Condition #4: Accuracy
As with loshon hora, one may not exaggerate rechilus even for a constructive purpose. If a person harmed or is planning to harm, someone else and the victim must be informed, one may not give him an exaggerated account of what has transpired or is about to occur. This applies even if the person being warned does not take the danger of the situation seriously.
Furthermore, one may relate only as much information as necessary for the purpose to be accomplished. To relate any additional information would be a transgression of the prohibition of rechilus.
Condition #5: Pure Intent
By commanding us, “Do not go as a gossipmonger among your people” (Vayikra 19:16), the Torah is teaching us that to derive pleasure from spreading gossip runs contrary to the mature, dignified character expected of a Jew. Thus, one who derives pleasure from spreading gossip has violated this commandment even when his report brings about a constructive result.
Relating what would otherwise be considered rechilus for a constructive purpose is permissible only if one’s intent is solely to accomplish that purpose. Deriving satisfaction from being “involved in the action,” or from aborting the plans of someone who is not well-liked, is forbidden.
Nevertheless, improper motivation cannot free one of his obligations to impart information for a constructive purpose. The Torah demands that we develop a correct mind-frame and come to the aid of our fellow Jew out of sincere concern.
Condition #6: Weighing the Options
As with loshon hora, one may not relate rechilus for a constructive purpose if this purpose can be accomplished through other means (see Day 46).
Of course, easiest of all is the direct approach – informing the potential victim of what is being plotted and allowing him to fend for himself. The Torah, however, views this avenue as a last resort. If the option exists, one must protect the victim without his even suspecting that someone is attempting to harm him. (This option does not apply where it is important for the potential victim to be on guard should the other party attempt to harm him at a later point in time.)
Obviously, there is a limit to how much effort one is required to invest in protecting his fellow Jew from harm when the person is fully capable of protecting himself. If, in order to avoid involving the potential victim, one would have to dedicate an unreasonable amount of time and energy, it would be permissible to inform the person so that he can protect himself.
Condition #7: No Revenge
The final condition necessary to permit speaking what would otherwise be rechilus for a constructive purpose is that conveying the information does not cause undue harm to the subject. Constructive intent does not justify causing harm to another person.
Therefore, one cannot inform a person that someone else is about to harm him if the person will respond by harming the plotter. This applies not only to physical or financial retaliation but even to retaliation in the form of loshon hora in a manner prohibited by halachah.