Symbols God used reveal HE perfectly knows our psychology, also reveal secret to us on how to live with ease and peace

Do not share spiritual knowledge with dogs (Mathew 7:6)

"Outside are the dogs, those who practice magic arts, the sexually immoral, the murderers, the idolaters and everyone who loves and practices falsehood." (Revelation 22:15) Out of six traits, two (dogs and magicians) are given as symbolic, in harmony with the overall spirit of Revelation what was "signified (sémainó)" or given in signs/symbols. (Revelation 1:1, biblehub.com)

Dog is symbol of doing things fast—it walks, breathes, eats fast,# in the process it eats even its own vomit without benefiting from its own best skill [smelling]. Thus, a dog is the symbol of seeking things of God [rather than God], in such hurry and worry, desire is felt strongly which gives birth to primary vices. (Details HERE) Thus dog is symbol of non-spiritual people, disregarding even those placed in authority, (2 Samuel 16:9), disregarding spiritual knowledge (Mathew 7:6), putting "confidence in flesh" rather than in God. (Philippians 3:1-3) Dog leaves its sign of passing by urinating on every object, even on wheels of parked vehicles. Thus dog perfectly symbolizes people who have a mistaken view that they have come here to convince others that they are better than others, thus do everything to leave their MARK so that others should remember them, thus symbolize “the first” or the prominence-seekers about whom Jesus said "Many who are first will be last, and the last first.” (esv.org/verses/Matthew+19:27-30, details HERE)

Dog is very sensitive as it gets disturbed by everything that happens around it and disturbs the peace of passersby. It walks ahead of its master as though it knows everything. When people disregard Laws of God, guess answers to mysteries of life, they are as though walking ahead of their Master/God—that too when we are already steeped in mysteries (Google: biggest-unsolved-mysteries-in-physics), thus unwittingly pollute our only habitat, earth (Revelation 11:18) causing even climate emergency. Life would come in ease and peace if you identify dog-like people and stop correcting them, commenting about them etc.

b) Hence next symbol [magicians] is placed immediately after Dog. Those who "practice magic arts." The Greek word used is φάρμακοι (pharmakoi) "magicians" (biblehub.com) who are symbol of believing in the MAGIC of MATTER saying universe, life, consciousness ... etc all originated from matter as play of particles/chemicals against all experienced truth. (Details HERE)

#Footnote--------------------------------------------------------------

Eating slowly and appreciatively with full focus on eating is described as sign of wisdom: "A desirable treasure will rest on the mouth of the wise; but foolish men will swallow it up." (Proverbs 21:20, Septuagint) It enables us to remember God, the real source of all food-provisions on earth, with appreciation. And the more we do this the more appreciative of God we become. If this is not taken as primary evidence of God, that person will not be satisfied with any other evidences. This explains why Jesus ignored atheism completely, why he also did not train his followers on how to reason with atheists.

Greek word for dog is κύων (kuón) which “looks like it has to do with the verb κυω (kuo), to be or make pregnant.” (Theological Dictionary, Abarim) Thus it symbolically denotes those who are “pregnant” with materialistic plans apart from God which becomes an obstacle for inheriting kingdom of God (Mathew 24:15-22; Luke 13:24) as they are too busy to develop appreciation for spirituality to the extent they are symbolically called "dead" towards God and towards joy of doing His will. (Mathew 8:22)

Why God uses symbols?

Symbols are sure messages, will not be misunderstood as they are common to all languages and nations. Hence too important messages and concepts come in symbols. For example,

Word for COMPASSION is linked with word for womb, thus "adjective רחום (rahum), meaning compassionate (Exodus 34:6, Deuteronomy 4:31). This word is always used for God's feelings towards man, from parent noun רחם (rhm; pronounced as rehem or raham), meaning womb (Genesis 49:25, Exodus 13:12, Jeremiah 20:17)" denotes "feelings of fraternal unity." (Theological Dictionary, Abarim) Thus reader readily relates how he must feel compassion deep within as womb is deep within, and how he should express in a way the recipient should feel she/he received new life as new life is formed in the womb. Hence such an attitude and behavior pattern is given as answer to the too vital question “What must I do to inherit eternal life?” and as description of “pure religion.” (Luke 10:25, 37; James 1:27)

Similarly, the word for SOUL and SPIRIT are linked with breathing IN and breathing OUT, sign of being alive. Thus reader readily remembers these words as denoting the higher entity that makes both Inhalation and Exhalation possible making the organism alive and functional and also remembers body turns into mere trash in the absence Soul/Spirit. “The Greek word noun ψυχη (psuche) comes from the verb ψυχω (psucho), meaning to breathe, or rather to draw breath. And word for Spirit “πνευμα (pneuma) likewise comes from a verb that has to do with breathing out,” from “verb πνεω (pneo) means to blow.” (Theological Dictionary, Abarim). In the process, the reader also notes need of taking IN only what is nourishing to his life [as life-saving oxygen is taken in through inhalation] and the need of expelling all harmful things from within [as carbon dioxide is given out through exhalation]. Thus reader is reminded to bring IN “fruit of The SPIRIT” and breathe OUT “works of flesh” (Galatians 5:19-23) which is the requirement for “the Kingdom of God.”