Basically: "Murdering babies is a good time."

Historical context: The writer has been exiled from Babylon. The Hebrew here is mournful; this psalm is often set to music.

What more conservative readers might say: It's a metaphor wherein the babies are "the sadness of the Babylonian exile" who should be “dashed against the rock of faith," or "dashing your sins against the rock of reason."

What more liberal readers might say: Noted Hebrew Bible scholar Robert Alter writes, "No moral justification can be offered for this notorious concluding line. All one can do is to recall the background of outraged feeling that triggers the conclusion.”

NB: The terms "liberal" and "conservative" here are used theologically, and used throughout as broad, non-exclusive simplifications, as the nuances of centuries of biblical interpretation are impossible to fully explicate here.



In general, "conservative" is used throughout to denote a more traditional approach that treats the biblical text with some measure of divine inspiration, whereas a "liberal" perspective might be more interested in a historical-critical approach that views the text as a document, or literarily.