Megillah, Chapter 4, Mishnah 9. The Mishnah continues to deal with practices that are improper in prayer and in translation, whether because they smack of heresy or for other reasons.
"Yevarechucha tovim" - this is the way of heresy:
One who uses this wording in his prayer is speaking in the manner of the heretics. Why is this so, and what does the phrase mean? Several explanations have been offered:
Only good people will bless You, but not the wicked. This is how Rashi explains it, and it is not our belief, for every person is obligated to bless the Holy One, Blessed is He.
It implies that Hashem is the G-d of the good alone.
"Tovim" does not refer to good people, but to those for whom life is good, as if only they bless Hashem. Yet we learned in the Mishnah in Berachos that every person is obligated to bless Hashem, both for the good and for the bad.
Three formulations for which we silence the one who says them:
"Al kan tzippor yagi'u rachamecha" - one who says in his prayer that the Holy One, Blessed is He, should have mercy on us just as His mercy extended to the bird's nest, where He commanded that the mother be sent away. We do not say this, because the mitzvos of the Holy One, Blessed is He, are decrees, and they do not stem from a motive of mercy alone.
"Al tov yizacher shemecha" - as if to hint that when something is not good, Hashem's Name should not be mentioned.
"Modim modim" - one who repeats the berachah of thanksgiving twice appears to be acknowledging two powers.
In each of these three cases, one who does so is silenced.
One who uses euphemisms in the passage of forbidden relations:
One who takes the passage of forbidden relations, which deals with prohibited intimate relationships, and translates it by way of a euphemism - that is, that the intent is not to actual marital relations but to disgrace, that one should not shame his parents and should not shame the rest of his relatives - he too is silenced, because he detracts from the true meaning of the halachah.
One who translates the verse about Molech:
The Torah states, "U'mizar'acha lo sitein leha'avir laMolech", and some explain that this is a form of idolatry of a different sort. But one who translates this verse mistakenly, saying that it refers to the prohibition of relations with a gentile woman - something that is true in itself, but is not the meaning of this verse - is silenced with a rebuke, because he takes the words of the Torah and understands them incorrectly.
Put simply, one who has relations with a gentile woman, though his sin is terrible, has not done something that carries the death penalty; whereas Molech, which is what the verse is speaking about, is a matter that carries the death penalty. It turns out that this translator is in fact altering the laws of the Torah. Even though he appears to be stringent, in the end there is an alteration of the Torah's laws here, and therefore he must be silenced.