Mishnayos Machshirin Perek 1 Mishnah 1

כל מעשה שתחילתו לרצון (a liquid the contact with which is welcome at first) – that it is satisfactory (i.e., rainfall) for it with those liquids, in order that the dish be rinsed or for other usages.

אע"פ שאין סופו לרצון (though finally it may be unwelcome/injurious) – when it fell on the fruit/produce, it was not satisfactory for it, even so it is that which makes it fit to become ritually unclean. Alternatively, it may finally be welcome, when they fell upon the fruit/produce. But at the beginning of their coming, the matter was difficult in his eyes, everything is fit to become ritually unclean.

הרי זו בכי יותן – that is to say, the foods that these liquids fell upon, are made fit to become ritually unclean from here and onwards. For no food is susceptible to receive ritual defilement until water or one of the seven liquids (see Tractate Makhshirin, Chapter 6, Mishnah 4) which are water, wine, [olive] oil, milk, honey, blood and dew, as it is written (Leviticus 11:38): “that if water is put on the seed and any part of a carcass falls upon it, it shall be impure for you; it is written as "יתן" but we read it as "יותן". Just as "יתן"/he will place is satisfactory for it, even something "יותן"/that is placed upon it is satisfactory for it.

מטמאין לרצון ושלא לרצון – since they are impure, their defilement and their fitness to become unclean come together as one, and if they (i.e., one of the seven liquids) fell on the fruit, even not being welcome, they defile them, for we don’t require that it is satisfactory for it but rather, that the liquid comes prior to the defilement, as it is written (Leviticus 11:38): “that if water is put on the seed,” and afterwards “and any part of a carcass falls upon it.” But when the liquid and the defiling agent come together as for example that the liquids are defiled, we don’t require that it is satisfactory for it.