You ask me why I have no verses sent?
For fear you should return the compliment.

[Cur non mitto meos tibi, Pontiliane, libellos?
Ne mihi tu mittas, Pontiliane, tuos.]

Martial (AD c.39-c.103) Spanish Roman poet, satirist, epigrammatist [Marcus Valerius Martialis]

Epigrams [Epigrammata], Book 7, epigram 3 (7.3) [tr. Hay (1755)]
    (Source)

Compare to Epigram 5.73. (Souce (Latin)). Alternate translations:

Why I send thee, Pontilian, not one of my writings?
It is lest thou, too gen'rous, return thine enditings.
[tr. Elphinston (1782), 12.10]

Why, sir, I don't my verses send you,
Pray, would you have the reason known?
The reason is -- for fear, my friend, you
Should send me, in return, your own.
[tr. Webb (1879)]

Why do I not send you my books, Pontilianus? Lest you should send me yours, Pontilianus.
[tr. Bohn's Classical (1897)]

Why do I not send you my works, Pontilianus? That you, Pontilianus, may not send yours to me.
[tr. Ker (1919)]

You ask me why my books were never sent?
For fear you might return the compliment.
[tr. Pott & Wright (1921)]

Pontilianus asks why I omit
To send him all the poetry that is mine;
The reason is that in return for it,
Pontilianus, thou might'st send me thine.
[tr. Duff (1929)]

Why don’t I send you my little books?
Pontilianus, lest you send me yours.
[tr. Kline (2006), "No thanks"]

You ask me why I send you not my book?
For fear you'll say, "Here's my work -- take a look."
[tr. Wills (2007)]

Why don’t I send my books to you?
For fear you’d send me your books, too.
[tr. McLean (2014)]

Why send I not to thee these books of mine?
'Cause I, Pontilian, would be free from thine.
[tr. Wright]

You ask me why I’ve sent you no new verses?
There might be reverses.
[tr. Burch]

I never send my books, it’s true.
Know why? You’d send me your books too.
[tr. West, "Reply"]

You wonder why my little book is overdue,
dear Pontilianus?
It’s just that I don’t want to look at one from you.
[tr. Juster]