פירוש על קידושין 56:5

Generally speaking money cannot acquire—so why did this mishnah allow money to acquire (in this limited circumstance)? The answer is that from the Torah, money can acquire. The rabbis decreed that money does not acquire goods lest someone sell some wheat, take the money and then tell the other person that his wheat was burned. In other words, the law that money does not acquire was created for the protection of the buyer.