Eternal torment some sour wits foretell
For those who follow wine and love too well, —
Fear not, for God were left alone in Heaven
If all the lovely lovers burnt in hell.

Omar Khayyám (1048-1123) Persian poet, mathematician, philosopher, astronomer [عمر خیام]

Rubáiyát [رباعیات], Bod. # 127 [tr. Le Gallienne (1897)]
    (Source)

I am fairly certain I am conflating two different quatrains below, Bodleian 127 (which mentions hypocrisy in the second line), and one not found in that manuscript (see the Whinfield translations). But both conclude with the sentiment that if lovers and drinkers are to be sent to Hell, then Heaven will be empty. Further discernment is left as an exercise for the reader.

This quatrain(s) is also unique in FitzGerald only offering a single go at translation, and that in just the 2nd ed.

Alternate translations:

If but the Vine and Love-abjuring Band
Are in the Prophet's Paradise to stand,
Alack, I doubt the Prophet's Paradise
Were empty as the hollow of one's hand.
[tr. FitzGerald, 2nd Ed (1868), # 65; this does not appear in other editions before or after]

Folk say that there is a hell. This is a vain error, in which no trust should be placed, for if there were a hell for lovers and for bibbers of wine, why heaven would be, from to-morrow morn, as empty as the hollow of my hand.
[tr. McCarthy (1879), # 131]

If wine be an unpardonable sin,
God help Khayyam and his wine-bibbing kin!
If all poor drouthy souls be lodged elsewhere,
Heaven's plains must be as bare as maiden's chin.
[tr. Whinfield (1882), # 33]

Drunkards are doomed to hell, so men declare,
Believe it not, 'tis but a foolish scare;
Heaven will be empty as this hand of mine,
If none who love good drink find entrance there.
[tr. Whinfield (1883), # 67]

To drain the cup, to hover round the fair,
Can hypocritic arts with these compare?
If all who love and drink are going wrong,
There's many a wight of heaven may well despair!
[tr. Winfield (1883), #381]

With Tales of future pains men threaten me,
They say there is a Hell in store for thee; --
Love, if there is a Hell for all like us,
Their Heaven as empty as my Palm will be.
[tr. Garner (1887), 1.19]

To drink wine and consort with a company of the beautiful
is better than practising the hypocrisy of the zealot;
if the lover and the drunkard are doomed to hell,
then no one will see the face of heaven.
[tr. Heron-Allen (1898), # 127]

Better to drink, with fair maids wander free.
Than in deceit to practice piety;
If sots and lovers all in Hell will be.
Then who would wish the face of Heaven to see?
[tr. Thompson (1906), # 425]

Tis better here with Love and Wine to sit
Than to become the zealous hypocrite;
If all who love or drink are doom'd to Hell,
On whom shall Heaven bestow a benefit?
[tr. Talbot (1908), # 127]

Drinking wine and wooing fair ones
Is a better thing than the hypocrisy of fanatics.
If all who drink wine were to go to Hell
No one would then behold Paradise.
[tr. Rosen (1928), # 256]

Better to drink and dance with rosy fairs,
Than cheat the folk with doubtful pious wares;
Tho' drunkards, so they say, are doomed to hell,
To go to heaven with cheats who ever cares?
[tr. Tirtha (1941), # 10.88]

They say lovers and drunkards go to hell,
A controversial dictum not easy to accept:
If the lover and drunkard are for hell,
Tomorrow Paradise will be empty.
[tr. Avery/Heath-Stubbs (1979), # 87]