Musar su Salmi 6:7

It is well known that the bringing of the first fruits was accompanied by great rejoicing. Thus it is related in Bikkurim (3:3-4) that a flute led the procession while the Levites sang. Therefore I believe that it was for this reason that Scripture mentions melei’acha — the first fruits, which are brought with joy — and dim’acha — “tears.” For by means of these two emotions a person subdues the two women, Machalas and Lilis, depriving them of the authority to lure him into sin. And if one succeeds in withstanding them it said, “Give Me the firstborn of your sons.” That is, one’s first drop of seed will then be delivered into the realm of holiness. That is why Scripture states shortly thereafter, “And you shall be to Me men of holiness” (Shemos 22:30). For whoever guards his sign of the covenant is called “holy.” Therefore whoever has blemished his sign of the covenant should shed tears while praying. Then he will be able to subdue those “plagues among Adam’s offspring.” For the Gates of Tears were never locked (Berachos 32b). King David also says, “Every night I cause my bed to float with tears; I cause my couch to melt” (Tehillim 6:7). He says further, “My tears were my bread, etc.” (Tehillim 42:4).