Halloween is a custom of the nations. God Himself calls such things abominations, practices that He hates. If we strip away its façade of revelry and feasting, it is idolatrous false worship, honoring spirit beings that are not God. In addition, God never tells us to celebrate this day or in any way to honor the spirits of the dead.
Notice that He warns us not to be "ensnared to follow" the practices of the nations. A snare is a trap designed to catch an unwary animal. The trap itself is hidden, but what is visible is a kind of lure, an attractive trick designed to fool the prey into entering the trap. Once it takes the bait, the gate comes down, a hook comes out, or a spring slams closed on a limb, and the prey is trapped.
God is alerting us to the fact that heathen or ungodly practices—customs, ways of worship, traditions, celebrations—usually have characteristics that appeal to our human nature. They are the lures. We can become caught up in them before we are aware of it. God advises us to watch out for the hidden dangers, the appealing entrapments, that are designed into these holidays.
Many cultures have a form of Halloween in their tradition. It seems that most of this world's peoples desire to celebrate the dead. The holidays or feasts may vary from place to place, falling on different days and following different customs. The common denominator is that they all honor or remember the dead or unseen spirits.
Mexico has its "Day of the Dead" in which participants give out candies in the shape of skeletons and visit graveyards to commune with the dead by leaving them food. In Japan, they honor their ancestors with various celebrations. Certain African tribes set aside days to honor the unseen spirits, warding off the evil ones and placating the good. German, Scandinavian, Spanish, Italian, and many other cultures have a Halloween-type holiday.
In English-speaking countries, Halloween derives primarily from the Celtic festival of Samhain (pronounced "sow-in"). Samhain, held on the three days around November 1, was a kind of New Year's celebration and harvest festival all rolled up into one.
The Celts believed that these three days were special because of the transition from the old year to the new. They felt that during this time the boundary between the physical and spiritual worlds relaxed or lifted, allowing spirits to cross over more easily. This idea, of course, terrifies superstitious people—that departed spirits could walk among us, especially those who died in the past year as it was thought these spirits desired to return to the mortal realm. For this reason, they believed they had to appease the spirits to make them go into the spirit world and stay there.
The Celts did this by putting out food and treats so that, when these spirits came floating by their houses, they would pass on. They thought that, if they did not appease the spirits, they would play tricks or put curses on them. Whole villages would unite to drive away the evil spirits, ensuring that the upcoming year would be good. Others among them would hold séances or conduct other kinds of divination by incantation, potion, or trance to contact dead ancestors in hope of receiving guidance and inspiration.
An interesting aspect of this transition time—the three days of Samhain—is that it was considered to be "no time," a time unto itself. Thus, it became a tradition that the order and the rules by which people lived were held in abeyance during them.
All laws went unenforced. The social order was turned upside-down—the fool became king, and the king became the fool. Men dressed as women and vice-versa. People took on different personas, dressing in disguise and acting the part. No work was done during this period of total abandon, for it was a time for revelry, drinking, eating, making and taking dares, and breaking the law. In a word, it was chaos.
Then Roman Catholicism arrived on the scene and "converted" the pagans. It also decreed a day to honor departed saints: May 13, All Saints' Day. The priests instructed the "converted" pagans to keep All Saints' Day, but they continued to celebrate Samhain because it was so much more fun than attending church to pray for the hallowed saints of yesteryear.
To keep them in the fold, in AD 835 Pope Gregory IV officially authorized moving All Saints' Day to November 1 to coincide with Samhain. He allowed the pagan "Christians" to keep their old customs as long as they put a gloss of Christianity on them. Thus, they kept Samhain in the name of Christ to honor the departed saints.
Like Samhain, All Saints' Day began the evening before, which was called All Hallows' Eve, All Saints' Eve, or Halloween. Since then, Halloween has evolved into its present form, in which nothing remotely Christian remains. It is known for all its pre-Christian Celtic practices—particularly the recognition of the spirit world in the form of fairies, witches, ogres, goblins, demons, ghouls, vampires, etc.
Today, "trick-or-treating" is the most recognized of Halloween activities, and it is simply a form of extortion. Children, whether they know it or not, are acting as the spirits who will play a trick or put a curse on the one who does not pay up in food or treats. Divination and séances are also commonly held on October 31. Hooliganism—tricks resulting in vandalism—often reaches its high point on Halloween. For many years, Detroit was the scene of "hell night," in which rampaging young people trashed large areas of the city, setting fires, smashing cars and windows, looting, and generally creating havoc.
The Celtic feast of Samhain still survives in Halloween. It has simply reverted to our ancestors' Celtic practice.