חסידות אויף שמות 3:22

Because of this, we will only accept people who concern themselves with these matters into our association. Those who know that they do not belong to this category are asked to not join, so that they do not lead themselves and us astray, corrupting the other members of pure heart and clean thoughts.

as is possibly alluded to in the Midrash (Tanchuma, Balak 25) that Israel merited redemption from Egypt by virtue of their not "revealing their secrets" (the Hebrew word for "secret," "mistorin," connotes something that was previously hidden). They didn't just keep the secret of "Each woman will ask from her neighbor" (for valuables - the Jewish people were told a year before the exodus that they would be doing this, but didn't speak about it to their Egyptian neighbors); rather, they kept hidden all spiritual matters that are to be kept secret, for it is not appropriate that others should see exposed souls when they are purifying themselves. Contemplate this.

Regarding the verse "Come, let us deal shrewdly [with them], etc., lest they multiply, etc." And also [the phrase] "and join, etc., and go up from the land." There are two interpretations in Rashi, but they are really one.For behold, the Sages have taught that the Egyptian exile and all the exiles are for the purpose of elevating the holy sparks [nitzotzei kedushah] that are in all places, as we find [Genesis 13:10] "like the garden of the LORD, like the land of Egypt." If so, certainly there were hidden treasures there. And also regarding Joseph's words, the Sages hinted that he hid three treasures, etc. And certainly also the Egyptians—those wise men among them—understood this. Therefore they wanted to afflict the Children of Israel with hard labor so that they would not have the strength to extract "their prey" [these treasures] from their mouths. This is what is written: "lest they multiply"—for when good increases over evil, the good sparks are clarified from the mixture. "And when war befalls us"—meaning [war] with the side of holiness. "And join [nosaf] also"—this refers to that small light hidden that is found even among them [the Egyptians]. "And go up from the land"—that point [of light] through the ascent of the Children of Israel, as it says [Exodus 3:22] "and you shall despoil Egypt, etc."Regarding the two interpretations: There is a hint in the Masoretic tradition that the Ba'al HaTurim brings—"venosaf gam hu" [and also join] connects to [Proverbs 11:24] "yesh mefazer venosaf od" [there is one who scatters yet increases more]—that the scattering of Israel is only in order to add converts to them, as stated in the Gemara, and this is a hint to the holy sparks as mentioned above.[Exodus 1:12] "But the more they afflicted them [the more they multiplied]"—for according to the extent of the labor, Israel became stronger, as it says [Genesis 25:23] "and one nation shall be stronger than the other." And Rashi [explains]: Just as they set their heart to afflict, so did the Holy One Blessed be He set His heart to multiply, etc. The meaning is: it should have just said "increased and spread," but rather the Holy One repaid Israel according to the intention and thought of the wicked to afflict them, even though they did not succeed. With the wicked, thought is combined with deed [i.e., they are judged for their evil intentions]. And according to their evil thought, so did the Holy One calculate the good for Israel.