According to the grammarians, the prefix letter ב can be found in place of the letter מ. But the sages of blessed memory disagree.

And when it is written ושרף את הבגד...בצמר (And he shall burn the garment…of wool)⁷⁸⁰ they interpret the letter ב to mean composed of.

footnotes: ⁷⁸⁰ Leviticus 13:52.

And when it is written וזה לכם הטמא בשרץ (and these are they which are unclean to you among the swarming things)⁷⁸¹, where it is proper to say משרץ, they interpret the letter ב to mean the blood that is found inside of the שרץ.

footnotes: ⁷⁸¹ Leviticus 11:29.

For the Torah will not switch one prefix letter for another prefix letter, according to the opinion of the sages.