Bahá’u’lláh counsels Násiri’d-Dín Sháh to “judge…with truth concerning what hath befallen Him”

Look upon this Youth, O King, with the eyes of justice; judge thou, then, with truth concerning what hath befallen Him. Of a verity, God hath made thee His shadow amongst men, and the sign of His power unto all that dwell on earth. Judge thou between Us and them that have wronged Us without proof and without an enlightening Book. They that surround thee love thee for their own sakes, whereas this Youth loveth thee for thine own sake, and hath had no desire except to draw thee nigh unto the seat of grace, and to turn thee toward the right hand of justice. Thy Lord beareth witness unto that which I declare. 

- Bahá’u’lláh  (Quoted by Shoghi Effendi in ‘The Promised Day Is Come’)

Bahá’u’lláh explains to Násiri’d-Dín Sháh how He was chosen by God

The evanescent is as nothing before Him Who is the Ever-Abiding. His all-compelling summons hath reached Me, and caused Me to speak His praise amidst all people. I was indeed as one dead when His behest was uttered. The hand of the will of thy Lord, the Compassionate, the Merciful, transformed Me. Can anyone speak forth of his own accord that for which all men, both high and low, will protest against him? Nay, by Him Who taught the Pen the eternal mysteries, save him whom the grace of the Almighty, the All-Powerful, hath strengthened. The Pen of the Most High addresseth Me saying: Fear not. Relate unto His Majesty the Sháh that which befell thee. His heart, verily, is between the fingers of thy Lord, the God of Mercy, that haply the sun of justice and bounty may shine forth above the horizon of his heart. Thus hath the decree been irrevocably fixed by Him Who is the All-Wise. 

- Bahá’u’lláh  (Quoted by Shoghi Effendi in ‘The Promised Day Is Come’)

Bahá’u’lláh explains to Násiri’d-Dín Sháh that He didn’t study the “learning current amongst men”

The learning current amongst men I studied not; their schools I entered not. Ask of the city wherein I dwelt, that thou mayest be well assured that I am not of them who speak falsely. This is but a leaf which the winds of the will of thy Lord, the Almighty, the All-Praised, have stirred. Can it be still when the tempestuous winds are blowing? Nay, by Him Who is the Lord of all Names and Attributes! They move it as they list. 

- Bahá’u’lláh  (Quoted by Shoghi Effendi in ‘The Promised Day Is Come’)

Bahá’u’lláh’s proclamation to Násiri’d-Dín Sháh: - His “lengthiest Epistle to any single sovereign”

As to Násiri’d-Dín Sháh, the Lawḥ-i-Sulṭán, despatched to him from Akká and constituting Bahá’u’lláh’s lengthiest Epistle to any single sovereign, proclaims: “O King! I was but a man like others, asleep upon My couch, when lo, the breezes of the All-Glorious were wafted over Me, and taught Me the knowledge of all that hath been. This thing is not from Me, but from One Who is Almighty and All-Knowing. And He bade Me lift up My voice between earth and heaven, and for this there befell Me what hath caused the tears of every man of understanding to flow.” 

- Shoghi Effendi  (Quoting Bahá’u’lláh in ‘The Promised Day Is Come’)

A “vehement apostrophe to Constantinople”

Moreover, in the Kitáb-i-Aqdas, is this vehement apostrophe to Constantinople: “O Spot that art situate on the shores of the two seas! The throne of tyranny hath, verily, been stablished upon thee, and the flame of hatred hath been kindled within thy bosom, in such wise that the Concourse on high and they who circle around the Exalted Throne have wailed and lamented. We behold in thee the foolish ruling over the wise, and darkness vaunting itself against the light. Thou art indeed filled with manifest pride. Hath thine outward splendor made thee vainglorious? By Him Who is the Lord of mankind! It shall soon perish, and thy daughters and thy widows and all the kindreds that dwell within thee shall lament. Thus informeth thee the All-Knowing, the All-Wise.” 

- Shoghi Effendi  (Quoting Bahá’u’lláh in ‘The Promised Day Is Come’)

Bahá’u’lláh counsels Sultán ‘Abdu’l-‘Azíz “not forgetful of the law of God”

Be not forgetful of the law of God in whatever thou desirest to achieve, now or in the days to come. Say: Praise be to God, the Lord of all worlds!” 

- Baha’u’llah  (Quoted by Shoghi Effendi in ‘The Promised Day Is Come’)