Given from the Catholic Broadcasting Station 2SM Sydney Australia
Choose a topic from Vol 3:
Because they have taken the prayer from different English translations of the New Testament. The Catholic version uses "who" as the relative pronoun; the Protestant version uses "which." In our days, the pronoun "which" is reserved rather for things than for persons. As used in the Protestant version of the "Our Father," therefore, it is obsolete. But its use as a personal pronoun instead of "who" was quite correct at the time the Protestant translation was made. It is a correct form of old English, used at the time by both Catholics and Protestants. Quite a common expression in Chaucer is such a phrase as "The Abbot which was a holy man." Protestants use an obsolete form, but it was quite correct when the translation was made, and is intended even now in a perfectly correct sense. No Protestant has any idea of regarding God as a thing rather than as a person by his use of the word "which."
That is because usage has restricted it to inanimate things so long as you can remember. But, although you have always understood it to refer only to inanimate things, the word itself has not always been applied only to inanimate things in the English language.
It is because they have learned the "Our Father" from their Protestant Bible just as it is written there. But merely because they use a quite legitimate form of English which happens to be a little archaic now, we must not suggest that they are treating God with contempt as an inanimate thing. No good Protestant who says the "Lord's Prayer" would dream of doing that.