Is it sin for those who have made the covenant with God to celebrate a national holiday? Zechariah 8:19 gives four fasts established by the Jews, none of which has anything to do with God's plan. The fast of the fourth month (9th of Tammuz) marked when the Babylonians entered Jerusalem; that of the fifth month (9th of Ab), the destruction of the Temple; that of the seventh month (3rd of Tishri), the murder of Gedaliah, a governor of Judah; and that of the tenth month (10th of Tebeth), the beginning of the Babylonian siege of Jerusalem.
God nowhere says that they are evil, that He hates them, or that to observe them is sin. In fact, the prophecy in which these fasts appear shows not only God's approval of keeping them, but also that He will turn them into feasts of joy rather than fasts of sorrow.
One might argue, "Yes, but these fasts are solemn and serious in their purpose, and God could hardly be displeased with that." Maybe so, but is God displeased when people have fun rejoicing over His blessings? Hardly! The prophecy clearly shows He wants us to rejoice.
John W. Ritenbaugh
Thanksgiving or Self-Indulgence?