סימן סה סעיף טז
אָסוּר לִקְנוֹת תְּבוּאָה אוֹ שְׁאָר דָּבָר בְּהַקְדָּמַת מָעוֹת, וְשֶׁיִּתֵן לוֹ אֶת הַתְּבוּאָה לְאַחַר זְמָן, דְּחַיְשֵׁינָן שֶׁמָּא בֵּינְתַיִם תִּתְיַקֵּר הַתְּבוּאָה אַחַר כָּךְ בִּזְּמַן שֶׁיִּתֵּן לוֹ אֶת הַתְּבוּאָה, וְנִמְצָא הַלּוֹקֵחַ נוֹטֵל יוֹתֵר מִשִּׁעוּר מְעוֹתָיו בִּשְׁבִיל שֶׁהִקְדִים אֶת הַמָּעוֹת. אֲבָל אִם יֵשׁ לְהַמּוֹכֵר גַּם עַתָּה כָּל הַתְּבוּאָה שֶׁהוּא מוֹכֵר, אַף עַל פִּי שֶׁלֹּא יִתּנֶנָּהּ לַלּוֹקֵחַ עַד לְאַחַר זְמָן מֻתָּר, כִּי מַה שֶּׁיֵּשׁ לְהָאָדָם יָכוֹל לִמְכּוֹר אֲפִלּוּ בְּזֹל הַרְבֵּה כִּרְצוֹנוֹ, וַאֲפִלּוּ הַתְּבוּאָה לֹא נִגְמְרָה עֲדַיִן לְגַמְרֵי כָּרָאוּי, אֶלָּא שֶׁצְּרִיכָה עוֹד מְלָאכָה אַחַת אוֹ שְׁתֵּי מְלָאכוֹת, נֶחְשֶׁבֶת כְּאִלּוּ הִיא גְּמוּרָה וּמֻתָּר. אֲבָל אִם מְחֻסֶּרֶת עוֹד שָׁלֹשׁ מְלָאכוֹת, אָסוּר. (וְעַיֵּן בְּסִימָן שֶׁלְאַחַר זֶה הֶתֵר לְהַקְדָמַת מָעוֹת עַל סְחוֹרָה)
It is prohibited to buy grain or any other item by paying money in advance while the grain will be delivered at a future date, because it is possible that in the interim the grain price will increase by the time the delivery is made, resulting in the buyer getting more than [the value of] his money, because he advanced the money. However, if the seller now has in his possession all the grain that he is selling, though he will not deliver it to the buyer until a later date, it is, nevertheless, permitted, because a man may sell whatever he possesses at a very reduced price if he sees fit to do so.30Since the grain is now ready for delivery and the buyer could actually take possession of it now, then the increase in the value of the grain is not of benefit to him. It is as if the grain increased in value after it had already been in the buyer’s possession. [This applies] even when the grain is not yet completely ready but still needs one or two processes [for its completion]. Regarding the transaction, it is considered completed and is permitted. If, however, it lacks three processes it is prohibited.31If there is still much left to be done to complete the grain’s process, it cannot be considered as already available for delivery, hence the increase in value cannot be construed as taking place in the buyer’s possession. It, thus, becomes a loan with an increased repayment, or—ribis. (See following chapter for a permissible procedure for advancing money for goods).
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)