The secret of the religious custom of having gongs and bells in temples and churches lies in the great science of the Hindus, which is Mantra Yoga. In the first place, this custom unites several religions, since bells are rung in Christian churches, in the temples of the Hindus, and in Buddhist pagodas. Many think that it is a call to prayer, but from a mystical point of view it is something more than that. The idea of the mystic is to make his heart capable of resonance, that every voice that rises on earth or descends from heaven may have its re-echo in his heart. The Sufi prepares himself by his exercises of Zikr and Fikr to make his heart capable of producing that resonance that may be caused on earth or descend from heaven. When the centers of the body and faculties of the mind are prepared to produce that resonance, then they respond to every sound, and every time the bell is rung it has its re-echo in the heart of the mystic, and every center of his being begins to think of God and to feel God. Vibration is a greater stimulant than wine. Wine gives intoxication to the brain, but vibration produces ecstasy in the heart. Therefore Sufis have called it wine.

The custom of having flowers in the house of prayer and the custom of burning incense in the place of worship also exists in almost all religions and has existed in almost all periods. Color and beauty also have a power, an influence upon the mind and body, and those who can enjoy the beauty of color and the delicacy of the flower receive help by the way of the eyes. Its effect opens the heart, which then responds to the blessing from above. This shows that the beauty of the earth can be best used to obtain the blessing from heaven. The perfume of flowers or incense has a deeper effect still, because color and beauty are only reflected upon the heart through the eyes, but perfume and incense, rising through the breath, touch the heart, making it capable of spiritual exaltation. But nothing has a greater influence on the human soul than sound. Therefore hymns are sung in all churches, prayers are offered, and chants are recited, all in order to wake the spirit within to life, which enables the soul to respond to the perfection of God.