66:5 If an investment was made for a certain length of time and the businessman retained the money even after the due date, he must pay the investor profit for the additional time. The assumption is that money remains with the investor under the original terms, though it is preferable to write at the time of the original agreement that, if the businessman retains the money longer than the agreed-upon length of time, then it will continue under the original terms.
66:6 The text for a business contract ("shtar iska") should read as follows:
I, the undersigned, acknowledge receipt of (sum of money) from (name of investor) of (investor's city) under a business arrangement to last (length of time) starting from the date below. I commit to purchase for the sum mentioned below any kind of merchandise that appears the most likely to earn profit. This money takes precedence over my own money. Any profit that G-d will give me from this merchandise will be divided with half going to me and half to the aforementioned (name of investor). Any losses, G-d forbid, will likewise be divided equally between us. Immediately upon the conclusion of (length of time) from the date below, I commit to return to the aforementioned (name of investor) the principal and his share of the profits. I will only be believed regarding losses upon the testimony of two reliable witnesses. I will only be believed regarding the profit upon taking an oath. However, we have agreed to a condition that I may give him, instead of his share of the profits, the amount of (agreed-upon amount), after which he will have no claims against me. The remainder of the profits will then belong solely to me, however much they are. All the laws regarding the reliability of the owner of this document apply even after its due date. So long as I have not returned the agreed-upon money that is in my possession, these conditions apply. I have received a fee for my efforts. (Signature, date, location.) Signed in our presence, witnesses (signatures of witnesses).