Kiddushin 4 - Money Effective for Betrothal - Another Source
Two sources are needed to prove that a father keeps both the earnings and the money of his minor daughter's Kiddushin. One might think that she does not work to receive Kiddushin money, and thus the father keeps it. Alternatively, one might think that the father feeds her, and thus keeps her earnings.
Another source why money is effective for Kiddushin is "When a man takes a woman", because Efron said to Avraham, " Take this field from me" - for money.
Efron's reincarnation was Aravna, who sold the location of the Temple to King David honestly and generously, correcting Efron's deed.