לַמָּ֣ס מֵרֵעֵ֣הוּ חָ֑סֶד וְיִרְאַ֖ת שַׁדַּ֣י יַעֲזֽוֹב׃
דעם װאָס גײט אײַן קומט רַחמָנות פֿון זײַן חבֿר, אַפֿילו ער פֿאַרלאָזט די מורא פֿאַרן אַלמאַכטיקן.
Rashi
By one who withholds kindness from his friend Heb. למס, by one who withholds kindness. The “lammed” is a prefix, as in (Num. 26:54), “to the numerous one (לָרַב)”; “to the one who returns (?) (לָשָב),” and (Isa. 28:10, 13) “for a precept (לצו).” מָס too is an expression of a verb, like בָּא, comes: שָב, returns; גָר, dwells; these also are an expression of doing [i.e., the present tense]:
Rashi
who withholds kindness, who destroys it, like (Exod. 16:21), “when the sun grew hot, it melted (ונמס).”