Here’s a great post from Rod Decker:
A palindrome is a word or sentence that reads identically forward and backward, e.g., “Do geese see God?” The Greek palindrome inscription:
is from the Hagia Sophia. (In Greek, Ἁγία Σοφία is short for Ναός τῆς Ἁγίας τοῦ Θεοῦ Σοφίας, “Church of the Holy Wisdom of God.” This was an Eastern Orthodox church building in Constantinople, constructed in the fourth century. For over a thousand years it was the Patriarchal Basilica of Constantinople. It is now a museum.)
Written in modern orthography the palindrome reads,
Νίψον ἀνόημα μὴ μόναν ὄψιν
and means, “Wash your sin, not only your face.” I first found this palindrome in Bruce Metzger’s Reminiscences of an Octogenarian, 23.
The word palindrome is itself a Greek word, παλίνδρομος, a compound of πάλιν, “again” and δραμεῖν, “to run”/δρόμος, “a race, race course.” There were apparently many Greek palindromes current in the ancient world. Another example that I’ve run across is:
ἀμήσας ἄρδην ὀροφόρον ἥδρασα σῆμα.
“Having reaped I established a lofty-roofed monument.”
(This one I found in Lloyd W. Daly, “A Greek Palindrome in Eighth-Century England,” American Journal of Philology 102 : 95–97.)