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למען ייטב לך וגו'. אִם מִצְוָה קַלָּה שֶׁאֵין בָּהּ חֶסְרוֹן כִּיס אָמְרָה תוֹרָה "לְמַעַן יִיטַב לָךְ וְהַאֲרַכְתָּ יָמִים", קַל וָחֹמֶר לְמַתַּן שְׂכָרָן שֶׁל מִצְווֹת חֲמוּרוֹת (שם קמ"ב): למען ייטב לך וגו׳ THAT IT MAY BE WELL WITH THEE etc. — If in the case of an easy command which involves no monetary loss, Scripture states “Do this in order that it may be well with thee and thou mayest prolong thy days”, it follows à fortiori that this at least will be the grant of the reward for the fulfilment of commands which are more difficult to observe (Chullin 142a).