The "Land of Mystery" refers to Adrianople, and "this Resplendent Spot" is a reference to Akká.
64. Amongst the people is he whose learning hath made him proud ... who, when he heareth the tread of sandals following behind him, waxeth greater in his own esteem [#41]
In the East, the practice has been for followers of a religious leader, out of deference, to walk a pace or two behind him.
65. Nimrod [#41]
The Nimrod referred to in this verse is, in both Jewish and Islamic traditions, a King who persecuted Abraham and whose name became symbolic of great pride.
66. Ag̱ẖsán [#42]
"Ag̱ẖsán" (plural of G̱ẖusn) is the Arabic word for "Branches". This term is used by Bahá’u’lláh to designate His male descendants. It has particular implications not only for the disposition of endowments but also for the succession of authority following the passing of Bahá’u’lláh (see note 145) and of ‘Abdu’l-Bahá. Bahá’u’lláh, in the Book of His Covenant, appointed ‘Abdu’l-Bahá, His eldest son, as the Centre of His Covenant and the Head of the Faith. ‘Abdu’l-Bahá, in His Will and Testament, appointed Shoghi Effendi, His eldest grandson, as the Guardian and Head of the Faith.