"Let the righteous strike me, it is kindness" (141:5). What does this verse mean?

Here is what the words are. In Hebrew the first half of the verse is six words: let him strike me, righteous, kindness, and let him reprove me, oil, head. The Hebrew has no words for the WEB's it is or like; the WEB supplies them. The verb for strike is halam, which elsewhere is "They beat me" (Proverbs 23:35) and Jael's blow when "she struck Sisera" (Judges 5:26) (tap strike). The verb for reprove is the one in "Reprove a wise person, and he will love you" (Proverbs 9:8) (tap reprove). Kindness is chesed, the word the WEB often gives as loving kindness (tap kindness). Then comes "don’t let my head refuse it" (141:5) (tap refuse). The verse's last line, "Yet my prayer is always against evil deeds" (141:5), is also compact in Hebrew: for still, and my prayer, in their evils. The Hebrew has their, which the WEB doesn't show, and the psalm doesn't say whose. The Hebrew noun, ra'ah, is given by Brown-Driver-Briggs as "evil, misery, distress, injury", and also "ethical evil"; the WEB takes it as evil deeds. The psalm doesn't say more, and these notes don't choose a reading for it.