מִן־הַ֖מֵּצַֽר קָרָ֣אתִי יָּ֑הּ עָ֜נָ֗נִי בַּמֶּרְחָ֣ב יָֽהּ
From the straits I called God; God answered me with a vast expanse.
I put הַ֖מֵּצַֽר into a contemporary Hebrew dictionary and it does come out as "straits, isthmus", but I'm still unclear on the meaning of the passage. I'm reading the Tanakh on Chabad's website (where there's an option to toggle Rashi), but Rashi doesn't explicate it. I was wondering where you guys go to get explanations of what things mean? Why would this particular metaphor have been used, and what is it getting at?