1,509. Consecrating the Oldest or Youngest Daughter
Hilchos Ishus 9:9
Let’s say that a man has two pairs of daughters from two different wives and he is able to marry off each of them. If he consecrated one of them and, when accepting the kiddushin, told the prospective husband that he is consecrating his oldest daughter, the meaning is clear. While one could say that he meant the older of the older daughters, or the older of the younger daughters, or even the younger of the older daughters, who is older than the older of the younger daughters, we are not concerned. All of his daughters remain available except for the older of the older daughters, who is consecrated. Similarly, if he consecrates his youngest daughter, one could say that he meant the younger of the younger daughters, or the younger of the older daughters, or even the older of the younger daughters, who is younger than the younger of the older daughters, nevertheless they all remain available except for the younger of the younger daughters, who is consecrated. This is because “my oldest daughter” suggests the oldest bar none, while “my youngest daughter” suggests the youngest bar none.
Hilchos Ishus 9:10
A father’s word is believed regarding a daughter under the age of majority. If he says she has been consecrated, then she is prohibited to marry (anyone else).