Commentary for Kiddushin 125:13

Rava explains why Resh Lakish had to explain that our mishnah holds that wages are incurred from beginning to end and that therefore he also gave her an additional perutah. In the baraita, the man stated “in payment for.” Clearly the work was the betrothal money. Our mishnah teaches “on condition.” This teaches that “on condition” is an external stipulation; it is not the mechanism through which betrothal is contracted. Therefore, he must also give her an additional perutah.