You are the light of the world. A city set on a mountain cannot be hidden. Nor do they light a lamp and then put it under a bushel basket; it is set on a lampstand, where it gives light to all in the house. Just so, your light must shine before others, that they may see your good deeds and glorify your heavenly father. (Matthew 5:14-16)
"Anton LaVey, the founder of the church of Satan, himself declared 
that by dressing up, either by wearing a costume or by coloring oneself in celebration of Halloween, signifies that you allow Satan to own you.
He further said that when you adopt the pagan practices, you subconsciously dedicate yourself to the devil. He took joy in Christians who take part in the tradition, saying:
Ramirez, who said that when you dress up even as an angel or a mermaid for Halloween, “you give the devil the legal rights to change your identity.” Ramirez further warned that there’s a much darker reality in Halloween beyond costumes and candy. The former Satanist turned Christian pastor said in an interview on CBS News (October 20, 2018):
I am glad that Christian parents let their children worship the devil at least one night out of the year. Welcome to Halloween.
LaVey’s statement is corroborated by a former Satanist, John
I was a general to the kingdom of darkness in witchcraft. I would sit with the devil and talk to him like I’m talking to you today. It was that kind of communication. It was that kind of relationship." WallStreetJournal