When it is said
Say it when you learn that someone has been talking about you behind your back and you want to hit back.
It is short enough to say on the spot, before you answer anyone.
Where it comes from
Author by tradition
Among St Ephrem’s prayers
A Russian collection of St Ephrem the Syrian’s prayers, printed by the monastery of Pochaev in 2008, gives it as the 11th of his “prayers for various occasions”. The next prayer in the book is the Lenten prayer “O Lord and Master of my life”. Ephrem was a deacon from Nisibis who later lived in Edessa, and he died in AD 373.
Molitvoslov i Psaltir prepodobnogo Efrema Sirina (Pochaev, 2008), on Azbyka; Ephrem the Syrian, Wikipedia
Did he write it?
No one can say. Ephrem wrote in Syriac, yet a great many works under his name survive in Greek. The translator Ephrem Lash judged most of those Greek works to be later writings by monks, of many dates and many hands. The Russian books print this prayer as Ephrem’s and give no older source for it.
Ephrem the Syrian, Wikipedia; Archimandrite Ephrem Lash on St Ephrem’s Greek works (archived)
What the words mean
A longer form
The Russian prayer book prints the same prayer a little longer, among its prayers for when your neighbours revile you, under the heading “from the works of St Ephrem the Syrian”. There it also asks God to do them no evil because of His unworthy servant, and it ends by praising God.
The Scripture in it
… bless those who curse you, pray for those who mistreat you.
Bible text: Berean Standard Bible, public domain.
In Russian
Помилуй, Господи, тех, которые ненавидят меня и завидуют мне,
а также злословят меня и клевещут на меня;
и никто из них ни в сем веке, ни в будущем, да не потерпит ничего худого ради меня, нечистого,
но святи их милосердием Твоим и покрой их благостью Твоею, о Всеблагий!
From Molitvoslov i Psaltir prepodobnogo Efrema Sirina (Pochaev, 2008), prayer 11, on Azbyka.