Here it is in context. Please correct me, but, I'm reading this as a clear instruction to believe even an outright contradiction as truth if it is coming from a messenger.
"Consider thou and call to mind the time when Muḥammad appeared. He said, and His word is the truth: is a service due to God.’ And likewise are the daily prayer, fasting, and the laws which shone forth above the horizon of the Book of God, the Lord of the World and the true Educator of the peoples and kindreds of the earth.
It is incumbent upon everyone to obey Him in whatsoever God hath ordained; and whosoever denieth Him hath disbelieved in God, in His verses, in His Messengers and in His Books. Were He to pronounce right to be wrong or denial to be belief, He speaketh the truth as bidden by God. This is a station wherein sins or trespasses neither exist nor are mentioned. Consider thou the blessed, the divinely-revealed verse in which pilgrimage to the House is enjoined upon everyone. It devolved upon those invested with authority after Him
11 to observe whatever had been prescribed unto them in the Book. Unto no one is given the right to deviate from the laws and ordinances of God. Whoso deviateth therefrom is reckoned with the trespassers in the Book of God, the Lord of the Mighty Throne.
O thou who hast fixed thy gaze upon the Dawning-Place of the Cause of God! Know thou for a certainty that the Will of God is not limited by the standards of the people, and God doth not tread in their ways.
Rather is it incumbent upon everyone to firmly adhere to God’s straight Path. Were He to pronounce the right to be the left or the south to be the north, He speaketh the truth and there is no doubt of it. Verily He is to be praised in His acts and to be obeyed in His behests. He hath no associate in His judgement nor any helper in His sovereignty. He doeth whatsoever He willeth and ordaineth whatsoever He 110 pleaseth. Know thou moreover that all else besides Him have been created through the potency of a word from His presence, while of themselves they have no motion nor stillness, except at His bidding and by His leave."
Bahá'í Reference Library - Tablets of Bahá’u’lláh Revealed After the Kitáb-i-Aqdas, Pages 101-134