Generally speaking, according to Jewish law, a transfer of property between two parties can only be done by means of a kinyan. Our Gemara teaches us that there are times when a simple, verbal agreement can take the place of a formal kinyan. Specifically, Rav Giddel teaches that when the parents of a couple that is about to be married meet one another and promise to give a certain amount to their son and to their daughter, once the marriage takes place – hen, hen ha-devarim ha-niknin ba-amirah – these are things that are purchased with an oral statement.
The Talmud Yerushalmi comments on this law that it is true only if it is the fathers of the bride and groom who are making the promises, but that other relatives cannot effect a kinyan with just a verbal agreement. Furthermore, it would only be true if this was a first marriage. The reason behind these limitations appears to follow the reasoning of Rav in our Gemara’s conclusion. The kinyan works in our situation because the unique joy that accompanies the wedding has the ability to give greater power to the statements that are made than would ordinarily be the case. This is only true if we are dealing with parents and a first marriage. The Meiri adds that according to this logic, were the bride and groom themselves to make oral commitments, that should also fall into this category and obligate them to live up to their word.
Does the wedding need to take place immediately after the agreement in order for it to create this level of commitment? From the simple reading of the Gemara, it would appear to be so, since the Gemara uses the term amdu ve-kidshu – they got up and married – after the agreement. The Rashbam and the Re’ah both accept this position. The Ritva however, suggests that this expression simply indicates that when the wedding takes place, the oral agreement becomes a final commitment.