The phrase "على بيّنة من ربي" appears several
times in the Quran, specifically when different Prophets were arguing with
nonbelievers.
In Surat Al-An'am (ch. 6), Prophet Muhammad peace be upon him is addressed as follows
(Quran 6:57):
"قل إني على بينة من ربي"
Yusuf Ali's translation of (6:57): "Say: 'For me, I (work) on a clear Sign from my
Lord'."
Pickthall's translation of (6:57) : "Say: I am (relying) on clear proof from my Lord".
Imam Al-Razi (in his exposition, Mafateeh Al-Gaib) interprets "على
بيّنة من ربي" in his comment on (11:28), saying it means: "Knowing the
Essence of God and His Qualities".
Sufi shiekh Ibn Ajeeba (in his exposition Al-Bahr Al-Madeed) interprets
(6:57) as: "Say: I am on a
clear Path that leads to Realization of Knowledge of God, and being exposed to
the good pleasure of God "رضوان الله" (which is
described in Yusuf Ali's translation of (9:72), as the greatest bliss and
the supreme felicity), myself and those who follow me." A couple of paragraphs
later, he adds about the same phrase, that it points to "having a penetrating
insight which enables to clearly
see/experience the secrets of the Lord".