John Calvin Commentary Psalms 41:5

"Mine enemies speak evil against me, [saying], When will he die, and his name perish?" — Psalms 41:5 (ASV)

My enemies have spoken evil of me. To speak is here used in the sense of to imprecate. In this way describing the improper conduct of his enemies, he seeks, as has been stated elsewhere, to move God to have mercy on him, because the more God sees His own people cruelly treated, the more He is disposed to mercifully aid them.

Thus David, by his own example, stirs up and encourages us to greater confidence in God, because the more our enemies break forth in their cruelty towards us, the more it gains favor for us in God's sight.

The terms in which his enemies uttered this imprecation show how cruel their hatred had been towards him, since it could only be appeased by his destruction—and that, moreover, accompanied by shame and disgrace, for they wished that with his life the very remembrance of his name should also be blotted out.