"Wings that are besmirched with mire can never soar."

"O Shaykh! Enter thou My presence, that thou mayest behold what the eye of the universe hath never beheld, and hear that which the ear of the whole creation hath never heard, that haply thou mayest free thyself from the mire of vague fancies, and set thy face towards the Most Sublime Station, wherein this Wronged One calleth aloud: “The Kingdom is God’s, the Almighty, the All-Praised!” We fain would hope that through thine exertions the wings of men may be sanctified from the mire of self and desire, and be made worthy to soar in the atmosphere of God’s love. Wings that are besmirched with mire can never soar. Unto this testify they who are the exponents of justice and equity, and yet the people are in evident doubt."

-Bahá'u'lláh, Epistle to the Son of the Wolf . pp. 130-131