"We do not encounter only a violent God in the Book of Psalms, but also a
violent psalmist. In Psalm 137 the psalmist calls out “Blessed is the person who
will take and dash your infants against the rocks”. Chrysostom is clearly not
comfortable with curses and requests for revenge in the Book of Psalms. He
argues that these words did not come from the psalmist himself.15 He says that
the psalmist merely describes the feelings of the captives in exile! Chrysostom
then reminds his congregation that the New Testament teaches us differently:
namely that we should give food and drink to our enemies and that we should
even pray for those who abuse us (cf. Luke 6:28). By putting the pleas for
revenge in the mouths of the captives, rather than in the mouth of the psalmist,
Chrysostom argues that there is no conflict between the message of the Old and
the New Testament. It was customary for the ancient exegetes to always attempt
to harmonize the message of the Scriptures, since they believed that Scripture
interprets itself."

Interesting concerning St. John Chrysostom and Psalm 137.