To the conductor over the Gittith. This refers to what is said in the scripture (Joel 4:13) "Send forth the sickle, for the harvest is ripe." Rabbi Pinchas said in the name of Rabbi Chelkia, "To whom was it said, 'Send forth the sickle?' The angels said to God, and Rabbi said to Israel.
We do not sing about the harvest or the vintage, but about the Gittith (as it is written) [Psalms 8:1], 'For the Gittith.' The harvest refers to Babylon (Jeremiah 51:33) 'The daughter of Babylon is like a threshing floor at the time when it is trodden.' The vintage refers to Media, as it is said (Zechariah 9:13) 'For I have bent Judah as my bow, I have filled the bow with Ephraim.' Redemption was found in the four languages during the harvest, in the vintage, and in childbirth.
If a person passes over them at the wrong time, he loses them, and even their owners do not benefit from them at all. This is what is written (Joel 4:13) "Send forth the sickle, for the harvest is ripe." In the harvest (Jeremiah 49:9) "If grape-gatherers came to you." In childbirth (Micah 5:2) "Therefore will he give them up, until the time that she who travaileth hath brought forth."
In the balsam (Song of Solomon 8:14) "On the mountains of spices." Similarly, it is said (Joel 4:13) "Come down; for the press is full, the fats overflow." Everyone sees the Gittith. Joel speaks about it as it is said (Joel 4:13) "Send forth the sickle."
Isaiah speaks about it as it is said (Isaiah 27:2) "And it shall come to pass in that day, that a vineyard of wine, red and good, shall be planted." Asaph speaks about it as it is said (Psalms 81:1) "For the Gittith." David speaks about it as it is said, "To the conductor over the Gittith."