Not every statement made by people who do business together is significant.
The Gemara (65b) describes a situation where someone sold a field with a stipulation that he does not guarantee the sale (i.e. if someone with a lien on the field comes and collects it from the purchaser, the original owner is not obligated to make up the loss). When he saw that the purchaser was upset, and he realized that the purchaser was concerned that he might lose his investment, the seller assured him that if the field was taken, he would pay the value of the field as well as the investment that was made in the field and the produce that was lost. Ameimar rules that this promise has no legal standing and we view it merely as words of enticement or encouragement, not an obligation.
The simple reading of the Gemara appears to explain this ruling as based on who is making the condition. Asking for a guarantee on the field should be the responsibility of the purchaser, not the seller, so we view the seller’s promise as mere words of encouragement. The Ra’avad quotes the Ge’onim as offering a different approach. They argue that in this case the condition is made at the wrong time – it should have been included in the agreement at the very beginning of their business transaction and not after the transfer of property had already taken place.
The Gemara continues with a similar story. On his death-bed, a man arranges for a get to be written for his wife. (This was usually done if the man had a brother, but he had no children, and the husband wanted to save the widow from “falling” to yibum or participating in halitza.) When handing over the document to his wife, she heard him groan. Realizing that he was unhappy divorcing her she told him that there was no need for concern, since if he recovered she would remarry him. Here, too, Rav Zevid rules that we view the promise as a simple statement of reassurance, and that this is not a true commitment and she is not obligated to marry him.