הַרְחִ֣יבִי ׀ מְק֣וֹם אָהֳלֵ֗ךְ וִירִיע֧וֹת מִשְׁכְּנוֹתַ֛יִךְ יַטּ֖וּ אַל־תַּחְשֹׂ֑כִי הַאֲרִ֙יכִי֙ מֵֽיתָרַ֔יִךְ וִיתֵדֹתַ֖יִךְ חַזֵּֽקִי׃
Enlarge the place of thy tent, And let them stretch forth the curtains of thy habitations, spare not; Lengthen thy cords, and strengthen thy stakes.
Ibn Ezra
Enlarge the place of thy tent, because of the larger number of thy children.
Rashi
lengthen your cords These are thin ropes that hang at the bottom of tents, and that are tied to stakes called ‘chevills’ in French, which are thrust into the ground.