Epistle to the Son of the Wolf -- by Baha'u'llah

From the inside front cover:

This is the last major Tablet of Baha’u’llah – the last of the hundred books He revealed. It was written to a priest in Isfahan, Persia, called the “Son of the Wolf”, whose father had sent the two martyrs known as the “King of Martyrs” and the “Beloved of Martyrs” to their deaths. This priest had committed the unforgivable sin: he had violated the Covenant and blasphemed against the Holy Spirit; that is, he had hated, not the lamp, or the Prophet of God as an individual – either from ignorance or because he did not recognize Him – but the Light of God itself which the Prophet reflects. He had hated the Light in the lamp, and “this destruction of the Light, ”’Abdu’l-Baha says in Some Answered Questions,” has no remedy.”