One day the Greatest Holy Leaf noticed that Ruhu'llah and his older brother 'Azizu'llah were playing in the garden. She called them in and they sat in her presence. Also present were Mirza Badi'u'llah and Mirza Diya'u'llah, the two sons of Bahá'u'lláh who later joined hands with Mirza Muhammad-'Ali, the Archbreaker of the Covenant of Bahá'u'lláh. The Greatest Holy Leaf, often referred to as 'Khanum', asked them what they said to people when teaching the Faith.
'We tell them', Ruhu'llah answered, 'that God has manifested Himself.'
Surprised at this remark, Khanum told them that surely they could not say such a thing straight away to people!
'We don't tell this to everybody,' responded Ruhu'llah, 'we only say it to those who have the capacity to hear such a statement. '
'How would you know such people?' asked Khanum.
'We look into their eyes and then know whether we can give them the Message,' replied Ruhu'llah.
Khanum laughed heartily and then beckoned Ruhu'llah to come close and look into her eyes to find out whether she had the capacity for hearing such words. In obedience to her request Ruhu'llah sat down opposite the Greatest Holy Leaf, looked intently into her eyes and then said, 'You already believe in these words. '
Then it was the turn of the two sons of Bahá'u'lláh. Ruhu'llah went close to them, looked searchingly into their eyes and sadly said to Khanum, 'They are not worth looking into!'
Truly, Ruhu'llah was no ordinary child.
(Revelation of Baha'u'llah volume four, by Adib Taherzadeh)
https://bahai-library.com/rev_bahaullah_4/taherzadeh_revelation_bahaullah_4.txt