The memory of the just is blessed - Or, is a blessing.
But the name of the wicked shall rot - This is another antithesis; but there are only two antithetic terms, for memory and name are synonymous - Lowth. The very name of the wicked is as offensive as putrid carrion.

The memory of the just [is] blessed: but the name of the wicked shall (d) perish.
(d) Shall be vile and abhorred both by God and man, contrary to their own expectation, who think to make their name immortal.

The memory of the just is blessed,.... Men to whom he has been useful, either in temporals or spirituals, bless him, or wish all blessings to him while alive, whenever they make mention of his name; and after death they speak well of him, and pronounce him blessed; for such are had in everlasting remembrance; the memory of them is sweet and precious; their name is famous and valuable, and always spoken of with honour and commendation; see Psalm 112:6. The Jewish writers take it for a command, and render it, "let the memory of the just be blessed"; and say, that he that transgresses it breaks an affirmative precept; they make an abbreviation of the word by the initial letters, and join them to the names of their celebrated men;
but the name of the wicked shall rot; shall be forgotten, be buried in oblivion, and never mentioned: and though they may call their houses, lands, and cities, by their own names, in order to transmit their memory to posterity; yet these, by one means or another, are destroyed, and their memorials perish with them; see Ecclesiastes 8:10; and if their names are mentioned after they are gone, it is with detestation and abhorrence, as things putrefied are abhorred; so they leave an ill savour behind them, when the good name of the righteous is as precious ointment, Ecclesiastes 7:1. It is a saying of Cicero (a), that
"the life of the dead lies in the memory of the living.''
(a) Orat. 51. Philip. 9.

Both the just and the wicked must die; but between their souls there is a vast difference.

blessed--literally, "for a blessing," or praise.
shall rot--literally, "be worm-eaten," useless and disgusting.

Thus, as Proverbs 10:6 says how it goes with the righteous and the wicked in this life, so this verse tells how it fares with them after death:
The memory of the righteous remains in blessings,
And the name of the godless rots.
The tradition regarding the writing of זכר with five (זכר) or six points (זכר) is doubtful (vid., Heidenheim in his ed. of the Pentateuch, Mer Enajim, under Exodus 17:14); the Cod. 1294 and old printed copies have here זכר. Instead of לברכה, יברך might be used; the phrase היה לברכה (opp. היה לקללה, often used by Jeremiah), subordinate to the substantival clause, paraphrases the passive, for it expresses a growing to something, and thus the entrance into a state of endurance. The remembrance of the righteous endures after his death, for he is thought of with thankfulness (צל''ז = זכר צדיק לברכה, the usual appendix to the name of an honoured, beloved man who has died), because his works, rich in blessing, continue; the name of the godless, on the contrary, far from continuing fresh and green (Psalm 62:1-12 :17) after his departure, becomes corrupt (רקב, from רק, to be or to become thin, to dissolve in fine parts, tabescere), like a worm-eaten decayed tree (Isaiah 40:20). The Talmud explains it thus, Joma 38b: foulness comes over their name, so that we call no one after their name. Also the idea suggests itself, that his name becomes corrupt, as it were, with his bones; the Mishnah, at least Ohaloth ii. 1, uses רקב of the dust of corruption.