Deuteronomy 27:24

מכה רעהו בסתר [CURSED BE] HE THAT SMITETH HIS FELLOW SECRETLY — It is of slander that it here speaks (slander may be termed “smiting in secret”) (Pirkei DeRabbi Eliezer 53). — I have seen in the Work of R. Moses the Preacher; There are here eleven verses beginning with the words “cursed be” corresponding to eleven tribes. In allusion to Simeon, however, he (Moses) did not write down a formula beginning with “cursed be”, because he had no intention to bless him before his death when he blessed the other tribes (the tribe of Simeon is the only one not mentioned in chapter XXXIII. which contains the blessings that Moses bestowed on the tribes), therefore he did not want to curse him either.

אָר֕וּר מַכֵּ֥ה רֵעֵ֖הוּ בַּסָּ֑תֶר וְאָמַ֥ר כׇּל־הָעָ֖ם אָמֵֽן׃ {ס}        

Cursed be he that smites his neighbour secretly. And all the people shall say, Amen.