Sefer Tehillim
Tehillim Four

4:1 For the Conductor; with instrumental music. A psalm of David. 2 Answer me when I call, O G-d of my righteousness. You have set me free in distress; have mercy on me and hear my prayer. 3 O sons of men, how long will my glory be put to shame, will you love vanity, and seek deception? Selah. 4 But know that Hashem has set apart the pious one for Himself; Hashem will hear when I call to Him. 5 Tremble, and sin no more; say this within your heart, upon your bed, and be still. 6 Offer the sacrifices of righteousness, and put your trust in Hashem. 7 Many say: "O that we would be shown the good!" Lift up the light of Your countenance upon us, O Hashem. 8 You have put gladness in my heart, since when their grain and their wine increase. 9 In peace will I together (both) lie down and sleep; for You, Hashem, alone, make me dwell in security.

The Midrash says that the present psalm ws expressed in three forms of praise - by orchestration (Nitzuah), by instrumental music (Nigun) and by song (Mizmor).

"With instrumental music"... (binginot) pertains to the prophectic faculty, as it says, "And it came to pass, when the minstrel played, that the hand of Hashem came upon him" (2Melachim 3:15).

"For the Conductor"... (lamnatzeach) pertains to Him who is eternal (lanetzach); G-d's orchestration is eternally everlasting.

The Radak writes:

"It seems that the menatzeach (conductor) was the one in charge of the singers, and all the psalms were recited and chanted as directed by the conductor. There was also a conductor in charge of the musical instruments called Neginot, and a conductor for the istruments called Sehminit. The songs were chanted in unison with the playing of instruments, such that every instrument was related to a different soul-lifting melody. The different musical instruments used in the Beit HaMikdash included the lyre, the harp, cymbals, ram's horns and trumpets. There were also many different kinds of melodies: Alamot, Neginot, Maskil, Michtam, Shigyon, Nechilot, Shigyonot, and Gitit. In addition, there are many varieties of the instrument called Asor. It is not known whether or not the musicians who played the instruments where also the ones who sang.

"For the Conductor; with instrumental music"... It is usually necessary to activate the Ruach HaKodesh in oneself by means of music, but David would become aroused on his own as the Ruach HaKodesh rested upon him from the beginning. Hence "a psalm of David," which conveys that first came the inspiration for the psalm. The reason is that he was always in a state of trustful cleaving to G-d, so that no element of ssadness entered his heart. As he goes on to say, "For You, Hashem, alone make me dwell in security" (4:9). Although he was always engulfed by troubles and surrounded by the vindictiveness of his enemies, he strove to rise above despair and to rejoice in the Divine Presence. So he was worthy to have the Divine Presence rest upon him.

"When I call... You have set me free in distress"... When in the past I was in distress, You set me free. I ask for the same thing in the future - "Have mercy on me and hear my prayer." When one man benefits another, it is unbecoming for the benefactor to then turn about and wrong his beneficiary; and David says, similarly: O G-d, You have dealt me the measure of Your beneficence, so be merciful and hear my prayer. Because You are "G-d of my righteousness" - You have always vindicated me in the past and "set me free in distress" - today, too, extend Your lovingkindness to me. "Have mercy and hear my prayer."

According to the Talmud, David says to G-d:

"Master of the world! You set me free from every affliction that I brought upon myself. When I was in trouble on account of Bat-sheva, You gave me my son Shlomo; I concerned myself with the troubles that afflict the Jewish people, and You granted me the (right to start building the) Beit HaMikdash."
According to the Midrash, David said: O G-d, You must vindicate my righteousness, for I am from the tribe of Yehudah. As it says, "Hear, O Hashem, the voice of Yehudah" (Devarim 33:7).

"O sons of men, how long will my glory be put to shame, will you love vanity, and seek deception?"... King David turns upon his enemies with words of angry admonition for tyring to harm and humiliate him. He presents three arguments. One, cease because you are all "sons of men," and it does not befit men of good will to shame other men. Two, "how long will my honor be put to shame?" It is unbecoming to reap honor by dishonoring another person. Three, "how long will you love vanity?" Your cause is lost, your striving against me is futile. So why do you persevere in vain?

You are mortal "sons of men." How do you presume to shame me, the one for whom G-d rises to save?! (3:8). My afflictions are my badge of honor and my glory, and you proclaim them to be my shame. How little you understand, how lacking in wisdom you are! You speak as if you were angelic beings, but you are merely "sons of men."

"But know that Hashem has set apart the pious one for Himself; Hashem will hear when I call to Him"... King David continues to address his foes - He has separated him and has made it known who is His pious one (i.e. it is David himself), and therefore "Hashem will hear when I call to Him."

David tells his foes: G-d has afflicted me with suffering in order to cleanse me and thus render me worthy of being among the pious that are free of sin. So, it is not as you proclaim it to be - that "there is no deliverance for him in G-d" (3:3). On the contrary, "Hashem will hear when I call to Him."

"Tremble, and sin no more; say this within your heart, upon your bed, and be still"... Some commentaries explain that King David confronts those who vilified him on account of the sin of having taken Bat-sheva. "Tremble" with fear "and sin no more" with your evil talk against me. "Say this within your heart, upon your bed, and be still forever." That is: Attend to the sins you yourself have committed on your couches and you will then cease your invective against me.