Albert Barnes Commentary Psalms 78:63

"Fire devoured their young men; And their virgins had no marriage-song." — Psalms 78:63 (ASV)

The fire consumed their young men - Fire here may be regarded as an image of destructive war, as in (Numbers 21:28): For there is a fire gone out of Heshbon, a flame from the city of Sihon: it has consumed Ar of Moab, etc. The idea here is that the young people had been cut off in war.

And their maidens were not given to marriage - As the young people who would have entered into this relation were cut off in war. The marginal reading here is 'praised'; “The maidens were not praised.” This is in accordance with the Hebrew. The idea is, “Their virgins were not praised in nuptial songs;” that is, there were no marriage celebrations; no songs such as were usually composed on such occasions in praise of those who were brides. The Septuagint and the Latin Vulgate render this much less accurately, and much less beautifully, were not lamented.