Kiddushin 64 - Older Daughters and Younger Daughters

If one has two groups of daughters from two wives, and he says: "I gave my eldest daughter in betrothal to a certain man, but I do not know if it was the eldest daughter of the older ones, or eldest of the younger ones, or the youngest of the older ones - they are all prohibited to marry other men, except for the youngest daughter of the younger ones - says Rabbi Meir.

Rabbi Yosi says that they are all permitted to marry other men, except for the eldest of the older ones, for a man would not voluntarily put himself in a position of doubt.