According to the History channel, “Halloween’s origins date back to the ancient Celtic festival of Samhain. Celts believed that on the night before the new year, the boundary between the worlds of the living and the dead became blurred. On the night of October 31st they celebrated Samhain, when it was believed that the ghosts of the dead returned to earth. Celts thought that the presence of the otherworldly spirits made it easier for the Druids, or Celtic priests, to make predictions about the future.”

The Bible does not explicitly talk about Halloween. However, predictions of the future are considered fortune-telling and are the practice of witchcraft. God considers involvement in witchcraft to be an abomination. 

We are to separate ourselves from unholy things, “… For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness?” 2 Corinthians‬ ‭6‬:‭14‬ ‭NIV‬‬

Can you imagine saying to the Lord, let us go trick or treating together? That is what you do when you go out. You have the Holy Spirit in you, and we are to be holy “Be holy, for I am holy” 1 Peter 1:16   

“The acts of the flesh are obvious: sexual immorality, impurity and debauchery; idolatry and witchcraft; hatred, discord, jealousy, fits of rage, selfish ambition, dissensions, factions and envy; drunkenness, orgies, and the like. I warn you, as I did before, that those who live like this will not inherit the kingdom of God.”

‭‭Galatians‬ ‭5‬:‭19‬-‭21‬ ‭NIV‬‬

“Make every effort to live in peace with everyone and to be holy; without holiness no one will see the Lord.”

‭‭Hebrews‬ ‭12‬:‭14‬ ‭NIV‬‬