Is it true that studies of the Dead Sea Scrolls indicate that
the Sermon on the Mount is actually an ancient Essene prayer
dating to hundreds of years before the birth of Christ?
The short answer is "NO"...
There are points of similarity between the Sermon on the Mount and various known teachings and phrases in use at Qumran, but there is no single document that comes even remotely close in content/structure to the Sermon on the Mount.
On the leading DSS scholars, James C. VanderKam, notes the similarities in his recent book The Dead Sea Scrolls Today [DSST:167]:
Another section that offers several Qumran-sounding words and phrases is the Sermon on the Mount in Matthew 5-7. One of these expressions is "poor in spirit" (Matt 5:3; War Rule 14.7). Among the attitudes encouraged in the Sermon are avoiding the use of oaths (5:33- 37), which, according to Josephus (Antiquities 15.371), was an Essene trait, and the duty to turn the other cheek (5:38-39; Manual of Discipline 10.17-18). Moreover, the antitheses in the Sermon ("you have heard that it was said . . ., but I say to you . . .") remind one of the way in which the still-unpublished legal "letter" (Some of the Works of the Torah = 4QMMT) introduces disagreements between the sect and its opponents: "you know.... we think/say."It should be readily apparent that "Qumran-sounding words and phrases", "Essene traits", and "reminds one of..." formulas do NOT encourage you to equate the Sermon on the Mount with a specific Qumran document! [Note that the parallels to the Sermon come from different documents--the War Rule, Manual of Discipline, 4QMMT!]
Actually, the terminology of Qumran has more affinities with John's language, than with Christ's (e.g. sons of darkness and light).
Now, it should be mentioned here that 'similarities' and 'points of contact' between the DSS and Christianity mean VERY, VERY LITTLE. Consider this cautionary note by Gaster, one of the original editors of the DSS [The Dead Sea Scriptures, Theodor H. Gaster (ed.), Anchor/Doubleday:1976(3rd ed.), p.20].
In order to get this whole question into the right perspective, it should be observed that just as many ideas and phrases in the Dead Sea Scrolls as can be paralleled from the New Testament can be paralleled equally well from the Apocrypha and Pseudepigrapha of the Old Testament--that is, from the non-canonical Jewish 'scriptures' that were circulating between 200 B.C. and 100 A.D.--and from the earlier strata of the Talmud. Moreover, many of them find place also in the ancient doctrines of such sects as the Mandaeans of Iraq and Iran and the Samaritans, so that even if they have not come down to us through Jewish channels, we can still recognize in them part of the common Palestinian thought and folklore of the time. Accordingly, to draw from the New Testament parallels any inference of special relationship is misleading.So, I am not sure how somebody might have tried to 'use' these similarities on you, but the answer to your question is an unequivocal "NO"...
hope this helps,
glenn miller, 01/04/97