סימן סו סעיף א
הַנּוֹתֵן לַחֲבֵרוֹ מָעוֹת שֶׁיִּתְעַסֵּק בָּהֶן וְהָרֶוַח יִהְיֶה לַחֲצָאִין, וְגַם הַהֶפְסֵד יִהְיֶה עַל שְׁנֵיהֶם בְּשָׁוֶה, זֶהוּ נִקְרָא עִסְקָא וְאָסוּר, מִפְּנֵי כִּי הַחֲצִי מִמָּעוֹת אֵלּוּ הִיא מִלְוֶה בְּיַד הַמְקַבֵּל, שֶׁהֲרֵי הִיא בָּאַחְרָיוּת שֶׁלּוֹ וְהוּא נוֹטֵל אֶת הָרֶוַח, וְגַם הַהֶפְסֵד עָלָיו. וְהַחֲצִי הוּא פִּקָּדוֹן אֶצְלוֹ, שֶׁהֲרֵי הוּא בְּאַחְרָיוּת הַנּוֹתֵן, וְהוּא לוֹקֵחַ אֶת הָרֶוַח מֵחֲצִי זֶה, וְגַם הַהֶפְסֵד מֵחֲצִי זֶה עָלָיו. וְהַמְקַבֵּל שֶׁהוּא מִתְעַסֵק וְטוֹרֵחַ בַּחֲצִי הַפִּקָּדוֹן שֶׁהוּא שַׁיָּךְ לְהַנּוֹתֵן, זֶהוּ רַק מִפְּנֵי שֶׁנּוֹתֵן לוֹ אֶת הַחֲצִי בְּהַלְוָאָה, וַהֲרֵי רִבִּית וְאָסוּר. וְיֵשׁ הֶתֵּר לָזֶה, אִם הַנּוֹתֵן נוֹתֵן לְהַמְקַבֵּל אֵיזֶה שָׂכָר בִּשְׁבִיל הֶעָמָל וְהַטֹּרַח שֶׁהוּא מִתְעַסֵּק בְּחֶלְקוֹ. וְיֵשׁ לִקְצוֹץ, אוֹ שֶׁיִּתֵּן לוֹ מִיָּד בִּשְׁעַת נְתִינַת הַמָּעוֹת שְׂכָרוֹ. וְדַי אֲפִלּוּ בְּדָבָר מוּעָט (קעז).
Preface
If Reuven gives money to Shimon for investment purposes and they agree to divide the profits or losses of this investment, then, it is considered as if each invested half the money with each receiving the profits or losses from his respective half. Thus, the half of the money that is Shimon's responsibility is actually a loan to him to do with as he sees fit. The half that is Reuven's is considered a pikadon (פִּקָדוֹן), i.e., an object given for safekeeping from Reuven to Shimon. The result is that Shimon expends time and effort on Reuven's half, in return for the half that is on loan to him. This is ribis. The entire transaction is called iska.
If one gives money to another for a business, stipulating that the profits be divided equally and any loss incurred also be [shared] by both of them equally, this is called iska and is prohibited. [This is] because half of the money is considered a loan to the trader (recipient) for which he is responsible and out of which he receives the profits, and for which he also incurs the loss.2Since this would be the status of any money on loan to him. The other half is considered as a deposit for safekeeping, for it remains the responsibility of the investor,3I.e., the original owner of the money. and he receives the profit from this half, and also incurs the loss from this half. The trader preoccupies himself and bothers with the pikadon half which belongs to the investor, only because he gives him half [the money] as a loan; this is ribis and prohibited. This transaction can be made legal by the investor giving the trader some compensation for the effort and bother [that he expends] when dealing with his share.4By being compensated for his effort, it can no longer be said that the trader is working as payment for the loan of his own half of the money. [The compensation] should be set [beforehand], or paid immediately upon the transfer of the monies. Even a nominal payment is sufficient.
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.)