We dabble in the Qur’án now and then,
Read, and repent, yet fall from Grace again;
But in the goblet is engraved a text
That greets eternally the eyes of men.

قرآن که بهین کلام خوانند اورا
گه گاه نه بر دوام خوانند اورا
در خطِ پیاله آیتی روشن هست
کاندر همه جا مدام خوانند اورا

Omar Khayyám (1048-1123) Persian poet, mathematician, philosopher, astronomer [عمر خیام]
Rubáiyát [رباعیات], Bod. # 6 [tr. Talbot (1908)]
    (Source)

(Source (Persian)). Alternate translations:

The Koran, which men call the Holy Word, is none the less read only from time to time, and not with steadfast study, while on the lip of the cup there runs a luminous verse which we love to read always and ever.
[tr. McCarthy (1879), # 24]

Men say the Koran holds all heavenly lore,
But on its pages seldom care to pore;
The lucid lines engraven on the bowl, --
That is the text they dwell on evermore.
[tr. Whinfield (1883), # 7; elsewhere # 10]

The Koran's word, oft called "the word sublime,"
Is seldom read, and not in every clime;
But on the goblet's rim there is a verse
Men read in every place and through all time.
[tr. Garner (1898), # 23]

The Koran, though The Word Sublime folk style it.
But here and there they read and once-a-while it:
Upon the cup-marge there's a bright verse written,
All-where-and-when folk read, though some revile it.
[tr. Payne (1898), # 20]

The Qurán which men call the best word
They read at intervals but not continually
On the lines upon the goblet there is a luminous text
Which they read at all times and in all places.
[tr. Heron-Allen (1897), Calcutta #6]

The Qur'an, which men call the Supreme Word,
they read at intervals but not continually,
but on the lines upon the goblet a text is engraved
which they read at all times and in all places.
[tr. Heron-Allen (1898), # 6]

Men call the Koran, God's Almighty word,
Yet read it rarely, or forget it quite;
Yet doth a graven verse the cup engird
That all men con, and all their tongues recite.
[tr. Cadell (1899), # 3]

Men call the Koran "Fount of Sacred Lore,"
"The Word Supreme," and, hasty, glance it o'er;
But on the goblet's rim a text is writ
That all shall read and ponder evermore.
[tr. Roe (1906), # 47]

The Koran though as "Word sublime" read o'er.
Men sometimes on its page, but not long, pore;
There is a bright verse in the cup's lines, for
Within men everywhere read, evermore.
[tr. Thompson (1906), # 6]

The Qur'án, which people call the Best Word, they
read it from time to time, not constantly
On the lines of the cup a sacred verse is engraved
which they read everywhere and always.
[tr. Christensen (1927), # 41]

The Koran they call the best of texts,
Yet oft-times they do not read it with application.
Around the goblet is engraved a verse
Which everywhere is read incessantly.
[tr. Rosen (1928), # 4]

"The scriptures are divine" thus we declare,
We read them seldom, kiss them oft and swear;
But in this cup of life, lo! shines the Word! --
The Truth unchained by bounds of when and where.
[tr. Tirtha (1941), # 9.12]

They call the Koran the Ultimate Word,
They read it occasionally but not all the time;
A text stands round the inside of the cup,
This they con at all times and in all places.
[tr. Avery/Heath-Stubbs (1979), # 145]