Barahin-e-Ahmadiyya-Parts1-2

Part two
of the Aryas towards which they invite all Hindus. But, strangely
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found wanting because, in their time, spiritual deterioration had not
reached such an extent as to require perfect revelation, whereas at the
time of the holy Quran they had all reached their extreme. This is why
the holy Quran stands apart from all other scriptures, which, even if
they had not been tampered with, were imperfect at the outset, and
always left room for the perfect teaching. however, there is no room
for any further teaching after the holy Quran, as there is no stage
beyond perfection.
But if it is supposed, for the sake of argument, that there might
come a time when the teachings of the Quran are replaced by those of
idolatry, as happened in the case of the Vedas and the Gospels, and the
concept of God’s oneness is changed and interpolated, and the millions
who strictly abide by the principle of divine Unity turn into polytheists
and idolaters, in such an eventuality a new law and new Prophet
would surely be required. Both these assumptions, however, lie outside
the realm of possibility. It is impossible for alteration or interpolation
to find its way into the holy Quran, as Allah the Almighty has himself
promised to safeguard it:
That is: ‘Most surely We have revealed this Book and We alone shall
forever remain its Guardian.’ (Surah al-Hijr, Part no. 14) ‡
The last thirteen hundred years bear witness to the truth of this
prophecy. No idolatrous teachings have ever been able to infiltrate into
the holy Quran and there is no logical reason to suppose that this will
ever happen in the future. hundreds of thousands of Muslims know
the whole of the Quran by heart, thousands of commentaries have
been written upon it, its verses are read in Prayers five times every
day. It is recited by its followers daily, millions of its copies have been
spread throughout the world, and its teachings have become known
to the people of every nation. All these things compel sane reason to
believe that it is impossible for any kind of interpolation or alteration
to ever find its way into the holy Quran.
‡ Surah al-Hijr, 15:10 [Publishers]