The Valley of Unity

In like manner, colors become visible in every object according to the nature of that object. For instance, in a yellow globe, the rays shine yellow; in a white the rays are white; and in a red, the red rays are manifest. Then these variations are from the object, not from the shining light. And if a place be shut away from the light, as by walls or a roof, it will be entirely bereft of the splendor of the light, nor will the sun shine thereon.
Thus it is that certain invalid souls have confined the lands of knowledge within the wall of self and passion, and clouded them with ignorance and blindness, and have been veiled from the light of the mystic sun and the mysteries of the Eternal Beloved; they have strayed afar from the jewelled wisdom of the lucid Faith of the Lord of Messengers, have been shut out of the sanctuary of the All-Beauteous One, and banished from the Ka‘bih of splendor. Such is the worth of the people of this age!
And if a nightingale soar upward from the clay of self and dwell in the rose bower of the heart, and in Arabian melodies and sweet Íránian songs recount the mysteries of God—a single word of which quickeneth to fresh, new life the bodies of the dead, and bestoweth the Holy Spirit upon the moldering bones of this existence—thou wilt behold a thousand claws of envy, a myriad beaks of rancor hunting after Him and with all their power intent upon His death.

Bahá'u'lláh The Seven Valleys