וְ֭אֵל הֵרַ֣ךְ לִבִּ֑י וְ֝שַׁדַּ֗י הִבְהִילָֽנִי׃
하나님이 나로 낙심케 하시며 전능자가 나로 두렵게 하시나니
Rashbam
מרך בלבבם, this does not mean that the heart has become soft, as in Deuteronomy 20,8 or as in Job 23,16, but the letter מ in the word מרך is an integral part of the word, not a preposition. In fact, even the emphasis is on that letter, as in the word אהל, tent. The word and its intonation is similar to Isaiah 58,13 וקראת לשבת עונג, and the word אוכל, ochel, which is intoned on the first syllable. The word מרך does not appear again in Scriptures.