Surah 25 ("al-furqân"), as it was transmitted, begins with the following verse:
For the Arabic text in Arabic script - presumably according to the Cairo standard edition of the Qur'an -, together with the comment (tafsîr) of four traditional exegets look at this Islamic site.
This traditional understanding presupposes the understanding of the word nadhîr as "warner". Both suppositions, the identification of furqân with the Qur'ân and the understanding of nadhîr as "warner", however are erroneous.
The classical Islamic understanding of the word furqân is al-faSl bayna l-haqq wa-l-bâTil, "separation between the truth and the vanity" (see Tabariy's commentary on this verse), which by lots of translators correctly is rendered by "criterion". This meaning "criterion", usually maintained for furqân, results from the attempt to interpret the Syriac purqân(â)/furqân(â), which has the meaning of "redemption, salvation", in a way that relates both to the Arabic word farq meaning "separation" and to the contexts in which the word furqân is found.
For evidence that the Syriac word furqân(â) or purqân(â) actually has the meaning "salvation, redemption", even precisely "price of redemption", I refer to these standard dictionaries of the Syriac language:
Carl Brockelmann, Lexicon Syriacum, Halle 1928 (reprint Hildesheim 1966), page 606
R. Payne Smith, Thesaurus Syriacum, vol. II, Oxford 1901, column 3295.
For your convenience I have marked the entry furqân(â) / purqân(â) by a thick perpendicular bar in the left margin of the shown sides of the dicitionaries.
As you may see, both dictionaries agree that furqân(â) / purqân(â) has the meaning of "liberatio" ("liberation"), "salvatio", "salus" (both meaning "salvation"), "redemptio" ("redemption") and especially "pretium redemptionis" ("price of the redemption").
As a learnt reader of my website, who is familiar with Jewish customs kindly pointed out to me, not only in Syriac (= Christian Aramaic), but also in Jewish Aramaic furqân(â)/purqân(â) is used in the sense of "salvation". The standard Jewish prayerbook, known as "The Complete Siddur" (ha Siddûr ha šalem), includes the prayer yeqûm purqan, "May salvation arise". According to a small explanatory footnote, provided in the here presented edition, the prayer was composed in Babylonia prior to the adoption by the Jews there of Arabic as their daily language - so certainly no later than the 800s. Besides for the noun form PRQN the prayer contains also the verb form yitparqûn, "may they be saved".
For the changing of the meaning from "redemption" through "criterion" to "revelation script" see Theodor Nöldeke, Geschichte des Qorans I, Leipzig 1909, p. 34; Neue Beiträge zur semitischen Sprachwissenschaft, Straßburg 1910, p. 23f.; A.J. Wensinck, Enzyklopädie des Islam, Leiden-Leipzig, 1913-1938, II, p. 126; Josef Horovitz, Koranische Untersuchungen, Berlin-Leipzig, 1926, S. 76; Jewish Proper Names and Derivatives in the Koran, Hebrew Union College Annual, vol. II, Ohio 1925, p. 145-227; Arthur Jeffery, The Foreign Vocabulary of the Qur'an, Baroda 1938, p. 225-229; Richard Bell, The Origin of Islam in its Christian Environment, London 1926, p. 118-125; Introduction to the Qur'an, Edinburgh, 1953, p. 136-138; W. Montgomery Watt, Muhammad at Medina, Oxford 1960, p. 16.
There are 7 places in the Koran where the word furqân is used: surah 2:50.181, 3:2, 8:29.42, 21:49 and 25:1. It has already been remarked long ago that in all places but in surah 25:1 the understanding of furqân as "salvation", "liberation", "redemption" etc.
The later and meanwhile traditional identification of furqân with the Qur'an is especially odd in surah 25:1. It is most highly improbable that already in the - according to the views of traditional Islamic scholarship - earliest "revealed" verses the book which allegedly did not yet exist already has been addressed, even by its supposed later name.
The general evaluation of the alleged meaning "the warner" for nadhîr is made possible by the etymological circumstances of this word. In all Semitic languages which functioned as vehicles for the transport of the Bible (and other religious material) to Arabia - Hebrew, Aramaic and Syriac - the root n-dh-r uniformly has the meaning of "to vow" or "that which is vowed". And so we have also in Arabic for the basic verb nadhara, in clear etymological relation to all other Semitic languages, the general and main meaning "to vow".
The noun nadhîr on account of its form fa'îl is a verbal adjective or noun of predominantly passive participle meaning. The Arabic dictionaries, at least partly, indeed register the primary meaning "vowed", "votive gift" or "consecrated to God" (see for instance P. Bélot, Al-Faraïd. Arabe-Français, 17e édition, Beyrouth 1955, p. 817, right column), others register "warner", as does the traditional Qur'an exegesis. This peculiarity is excused with the traditional comment that in this case the word of this pattern fa'îl has the meaning as if it were of the pattern muf'il (=mundhir, participle active of the IV. form of nadhara, which duly has the meaning "warner"). See for instance Lane, An Arabic-English Lexicon, London-Edinburgh 1863-1893.
The same lexica on the other hand report that the feminine variant of the masculine form nadhîr, which reads nadhîra, has the meaning "a votive gift": that which he gives who makes a vow, a child appointed by his parents by a vow to become a minister of the Church etc. (see Lane s.v.) This is quite peculiar: that the masculine noun nadhîr for those lexicographers should have a totally different meaning than the feminine noun of the same grammatical structure.
It can be seen from many phrases and examples of the usage of the word, how "to make someone vow" (IV. or causative form andhara) could change over to the meaning "to warn someone". Everybody who urges someone into a position where he has to make a vow brings this person into a difficult position and this can be paraphrased as "to warn him". But at the same time it becomes clear that "to warn" is not the real and basic meaning although it can - and this only with the causative (IV.) form andhara - get this secondary meaning in some cases.
Since nadhîr is a verbal adjective/noun of the basic
form nadhara - and not the causative (IV.) form andhara
it should originally not have had the meaning "warner", but the same
as registered for the feminine form nadhîra (which also
be understood as a nomen unitatis of the masculine noun), namely
gift" or "sacrifice". There is actually no text from pre-Islamic times
where nadhîr is used
with the meaning "warner". Passages in Old Arabic poetry -
taking aside the question of its genuinness - on the contrary use the
word in its etymologically correct meaning "something voted", "voted
gift", "devoted one" etc.
In the end we come to the original meaning of 25:1, namely:
Additionally, the rasm of 'âlamîna can be read as dual. And the dual "the two worlds" is theologically precise and correct since Christian theology sees the redemption brought about by Christ extending to the world of the living as well as to the world of the dead.
As a corollary we may remark: Also this verse displays the signs of the old pre-Islamic parts of the Qur'an, namely rhyme and metric pattern, as soon as one reads it as vernacular Arabic:
Blessed be He, who sent down the redemption
on His servant
that he might become a sacrifice for the (two) worlds.