יורה דעה קס״גYoreh De'ah 163

Se’if 1א׳

מִי שֶׁהָיָה נוֹשֶׁה בַּחֲבֵרוֹ מָעוֹת, וְאָמַר לוֹ: תֵּן לִי מְעוֹתַי שֶׁאֲנִי רוֹצֶה לִקַּח בָּהֶם חִטִּים, אָמַר לוֹ: צֵא וַעֲשֵׂה אוֹתָם עָלַי כַּשַּׁעַר שֶׁל עַכְשָׁו, וְיִהְיֶה לְךָ אֶצְלִי חִטִּים בְּהַלְוָאָה, אִם יֵשׁ לוֹ חִטִּים כְּשִׁעוּר מְעוֹתָיו, מֻתָּר אֲפִלּוּ לֹא יָצָא הַשַּׁעַר וְאִם לָאו, אָסוּר אֲפִלּוּ יָצָא הַשַּׁעַר (נ"י בְּשֵׁם רַמְבַּ"ן וְהָרַב הַמַּגִּיד שָׁם וְשֶׁכֵּן כָּתַב רַמְבַּ"ן וְרַשְׁבָּ"א) וְנֶאֱמָן הַמּוֹכֵר לוֹמַר שֶׁיֵּשׁ לוֹ, וְאֵין צָרִיךְ רְאָיָה לִדְבָרָיו (הַגָּהוֹת מָרְדְּכַי דְּאֵיזֶהוּ נֶשֶׁךְ), כְּדִלְעֵיל סִימָן קס"ב.

One who held a claim against his fellow for money, and said to him: give me my money, for I wish to buy wheat with it; and he said to him: go and make them over to me at the present rate, and you shall have wheat with me on loan — if he has wheat to the measure of his money, it is permitted, even if the rate has not come out; and if not, it is forbidden, even if the rate has come out (the Nimukei Yosef in the name of the Ramban, and the Rav haMaggid there, and that so the Ramban and the Rashba wrote). And the seller is believed to say that he has it, and he does not need proof for his words (Hagahot Mordechai on "Which is interest"), as above, siman 162.

Se’if 2ב׳

הֲרֵי שֶׁהָיָה לוֹ חִטִּים וְעָשָׂה הַלְוָאָתוֹ עָלָיו, וּבָא אַחַר זְמַן וְאָמַר לֵהּ: תֵּן לִי חִטִּים, שֶׁאֲנִי רוֹצֶה לְמָכְרָם וְלִקַּח בִּדְמֵיהֶם יַיִן. אָמַר לוֹ: צֵא וַעֲשֵׂה אוֹתָם עָלַי יַיִן כַּשַּׁעַר שֶׁבַּשּׁוּק עַתָּה, אִם יֵשׁ לוֹ יַיִן, הֲרֵי זֶה מֻתָּר. וְאִם לָאו, אָסוּר (ר"ן ונ"י).

If he had wheat and made his loan over upon it, and after a time he came and said to him: give me wheat, for I wish to sell it and to buy wine with the proceeds; and he said to him: go and make it over to me as wine at the rate that is in the market now — if he has wine, this is permitted; and if not, it is forbidden. (the Ran and the Nimukei Yosef)

Se’if 3ג׳

אָמַר לוֹ: הַלְוֵינִי מָנֶה. אָמַר לוֹ: מָנֶה אֵין לִי, חִטִּים בְּמָנֶה יֵשׁ לִי, וְנָתַן לוֹ חִטִּים בְּמָנֶה כְּמוֹ שֶׁהוּא הַשַּׁעַר וְחָזַר וּלְקָחָם מִמֶּנּוּ בְּצ', וַעֲדַיִן הֵם שָׁוִים מֵאָה (ב"י בְּשֵׁם ת"ר), אִם פָּרַע לוֹ לְבַסוֹף הַמָּנֶה בְּפֵרוֹת, מֻתָּר. אֲבָל אָסוּר לִפְרֹעַ בְּמָעוֹת, מִפְּנֵי הַעֲרָמַת רִבִּית, מֵאַחַר שֶׁאָמַר לוֹ תְּחִלָּה הַלְוֵנִי מָנֶה. וְאִם עָבַר וְעָשָׂה, הֲרֵי הוּא מוֹצִיא מִמֶּנּוּ ק ' בַּדִּין, שֶׁאֲפִלּוּ אֲבַק רִבִּית אֵין כָּאן. הַגָּה: וְיֵשׁ אוֹמְרִים דְּהָוֵי אָבָק רִבִּית. (טוּר בְּשֵׁם הָרַמְבַּ"ן וְהָרֹא"שׁ). וְכָל זֶה לֹא מַיְרֵי אֶלָּא כְּשֶׁלֹא הִתְנוּ מִתְּחִלָּה עַל כָּךְ, אֲבָל אִם הִתְנוּ מִתְּחִלָּה לִקְנוֹת מִמֶּנּוּ בְּפָחוֹת, הָוֵי רִבִּית גָּמוּר, (המ"מ פ"ה דה"מ בְּשֵׁם הָרַמְבַּ"ן וְהָרַשְׁבָּ"א, וְכֵן הוּא בְּנ"י), אֲפִלּוּ פָּרַע לוֹ פֵּרוֹת, אָסוּר (נימוק"י פ' א"נ).

He said to him: lend me a maneh (a hundred zuz). He said to him: a maneh I do not have; wheat to the value of a maneh I do have. And he gave him wheat to the value of a maneh as the rate stands, and went back and bought it from him for ninety, while they are still worth a hundred (Beit Yosef in the name of T"R): if he repaid him the maneh at the end in produce, it is permitted; but it is forbidden to repay in money, because of a subterfuge of interest, since he said to him at the outset: lend me a maneh. And if he transgressed and did so, he takes a hundred out of him by law, for there is not even the dust of interest here. Hagah [Rema]: And there are those who say that it is the dust of interest. (Tur in the name of the Ramban and the Rosh) And all this speaks only of where they did not stipulate about it from the outset; but if they stipulated from the outset to buy it from him for less, it is complete interest (the Maggid Mishneh, chapter 5 of the Laws of Lender and Borrower, in the name of the Ramban and the Rashba, and so it is in the Nimukei Yosef) — even if he repaid him with produce, it is forbidden (Nimukei Yosef, chapter "Which is interest").