It's good to have it on hand; it won't hurt to have it on hand
(Slang) Figuratively: even if there's no need for it right now, it's worth keeping within reach.
(Modern Hebrew)
Translation
Expression (Hebrew)
טוֹב שֶׁיִּהְיֶה בַּבַּיִת, לֹא יַזִּיק שֶׁיִּהְיֶה בַּבַּיִת
Definition (Hebrew)
(סְלָאנֶג) בְּהַשְׁאָלָה: גַּם אִם אֵין בּוֹ צֹורֶךְ כָּעֵת כְּדַאי שֶׁהוּא יִהְיֶה בְּהֶישֵּׂג יָד.
(הָעִבְרִית הַחֲדָשָׁה)