Halakhah zu Bereschit 23:16

If he gave her a Prutah and said to her “Be betrothed to me with this on the condition that I will give you a maneh.”¹¹²Originally the shekel was a unit of weight for means of payment in gold and silver. In the third millenium BCE one finds this unit of weight in Babylonia. Sixty Babylonian shekels were a maneh. When this system of coinage was introduced into Israel the maneh generally consisted of only 50 shekels. The shekel as a unit of weight for gold is first mentioned in Jewish sources in Genesis 24:22 and Joshua 7:21. In Genesis 23:16 one finds mention of the shekel as a unit of weight for silver. When the condition is fulfilled the betrothal will take effect retroactively even if he did not say “from now.” For anyone who says al menath it is as if he had said “from now.” Yet if she accepts betrothal from another before the conditions are fulfilled and afterwards the conditions were fulfilled, the betrothal of the second man is void. But if he said to her “on the condition that I will give to you a maneh within 30 days,” if he gave it to her within the thirty days behold it is a betrothal retroactively; if he did not give it within thirty days she is not betrothed, and if she accepts betrothal from another man during the thirty days she is betrothed but she is not betrothed¹¹³i.e., this is a pending situation. until thirty days. When the thirty days are completed if the conditions of the first man are not fulfilled the betrothal of the first man is cancelled and the betrothal of the latter is complete and she does not require a bill of divorce from the former. If the former fulfills his condition she does not require a bill of divorce from the latter.