The Catechism in Questions & Answers

307. What does the First Commandment mean for us today?

The First Commandment calls upon us to honour God out of love. We worship God in adoration, obedience, and the fear of God. The fear of God develops from our love for God. It is not an expression of fear, but of humbleness, love, and trust in God.
It is important to accept God as He has appeared to the world: in Jesus Christ (cf. John 14: 9).
It is a violation of this commandment to make a god, as it were, of power, honour, money, idols, or even one’s own person, to which all other things are subordinate. Likewise, it is a violation of the First Commandment to develop conceptions of God based on our own wishes or views. It is also a violation against this commandment to see gods in statues, trees, natural phenomena, etc. Beyond that, other acts that contradict the First Commandment include Satanism, fortune telling, magic, witchcraft, spiritualism, and necromancy.

The term ‘magic’ is derived from the Greek and translates to mean “sorcery”, or “illusion”. Magic also incorporates the notion that one can influence or control people, animals, and even events and objects by way of specific actions (rituals) and/or words (magical formulas). Magic is often associated with the evil one.
Fortune tellers are people who are convinced that they can see into the future or foretell future events. They make their predictions on the basis of mysterious signs which they interpret accordingly. At the time of the old covenant, fortune telling was common practice in the royal courts, however, it was strictly forbidden to the people of Israel.
Necromancy is a special form of fortune telling: those who practise it try to contact the dead in order to ask them about future events; cf. 1 Samuel 28: 3 et seq.

“Ascribe greatness to our God.”
Deuteronomy 32: 3