יִפְתַּ֣ח יְהוָ֣ה ׀ לְ֠ךָ אֶת־אוֹצָר֨וֹ הַטּ֜וֹב אֶת־הַשָּׁמַ֗יִם לָתֵ֤ת מְטַֽר־אַרְצְךָ֙ בְּעִתּ֔וֹ וּלְבָרֵ֕ךְ אֵ֖ת כָּל־מַעֲשֵׂ֣ה יָדֶ֑ךָ וְהִלְוִ֙יתָ֙ גּוֹיִ֣ם רַבִּ֔ים וְאַתָּ֖ה לֹ֥א תִלְוֶֽה׃
여호와께서 너를 위하여 하늘의 아름다운 보고를 열으사 네 땅에 때를 따라 비를 내리시고 네 손으로 하는 모든 일에 복을 주시리니 네가 많은 민족에게 꾸어줄찌라도 너는 꾸지 아니할 것이요
Or HaChaim on Deuteronomy
יפתח ה׳ לך את אוצרו הטוב, "G'd will open for you His store of goodness, etc." From this point on until the end of verse 13 the Torah describes the reward for fulfilling the positive commandments. This is why verse 13 concludes with the words "if you listen to the commandments of the Lord your G'd." The channels which G'd employs to direct the outpourings of His goodness to earth are activated through performance of commandments rather than through the passive refraining from violating negative commandments.
Rav Hirsch on Torah
V. 12. יפתח וגו׳, darum lässt Gott selbst die deine Bodenblüte bedingenden Witterungserscheinungen mit einer Regelmäßigkeit eintreten, die Sein unmittelbares Einwirken konstatieren, und gibt dir einen solchen Überfluss, dass, wenn anderwärts Mangel ist, du mit deinem Überfluss aushelfen musst, nie aber in die entgegengesetzte Lage kommst, und so
Chizkuni
והלוית גוים רבים, “and you will lend to many nations;” to nations who were plagued with crop failures or storage problems in their barns.