We have been asked whether a Jewish soldier may recite the well-known prayer from the Gospel of St. Matthew (Chapter 6) known as "The Lord's Prayer."
Judged merely by its content, this famous prayer has nothing objectionable in it to a Jew. In fact, almost every one of its phrases has been traced to Jewish sources or at least parallels have been found for them in Jewish sources. Nor is the fact that the prayer is of non-Jewish origin sufficient reason to prohibit its use by a Jew. A medieval legend found in a Midrash describes Simon Peter, the first of the Popes, as the author of various piyyutim used on the Day of Atonement (see Jellinek, "Bes Ha Midrash," V, 60ff; also "Kovetz Ma'asey Hagaonim," pp. 107-8). The only question involved is whether it is a violation of the law, "Thou shalt not follow their statutes." This law has already been described in previous responsa and the various limitations of it mentioned. It is only necessary to mention the fact that the law is careful to indicate that not necessarily everything which is customary among Gentiles should be avoided by Jews, but only such that either have no meaning (Da'as Hevel U' shtus) or those which are specifically part of their worship. See the explanation of Rabbi Isaac in the famous Tosfos to Avoda Zara 11a. Joseph Colon (Maharik, Italy, fifteenth century) says clearly, speaking of Christian garments, if a Jewish garment does not express Judaism or modesty any more than the garments which Gentiles wear, then there is no prohibition against the Jews adopting garments customary among the Gentiles (Maharik #88). This is cited by Joseph Caro in his "Kesev Mishnah" to Maimonides Hil. Akum XI, 1, and by Isserles to Yore Deah 178 #1.
If, however, the custom is generally a part of Gentile worship, then it is prohibited.
A fairly recent, clear statement on this is by Z'vi Dov Eisner in V'y'laket Joseph, Vol. IV #88, in which he says the prohibition against following their statutes applies only if the Jew does something which the Gentile does during the time of worshiping his God. Since "The Lord's Prayer," by its very title, refers to the prayer uttered by Jesus, and since it is a definite part of Christian worship, it certainly falls under the prohibition of following the statutes of the Gentiles and should not appropriately be recited by a Jewish soldier.
Of course, a Chaplain, when his duty requires of him to conduct non-Jewish worship, is under government command to do so, and that circumstance would fall under a different category.