As with most of Baha’u’llah’s Writings, He chose various instances to promote key ideas and concepts in His Revelation.  This passage is taken for a Tablet written to a man of Zoroastrian background who had asked him certain questions, to which Baha’u’llah responded with several remarkable Tablets published in the compilation “Tabernacle of Unity”,. The compilation is so-named because of this passage, also from these Tablets-

 Say: O well-beloved ones! The tabernacle of unity hath been raised; regard ye not one another as strangers. Ye are the fruits of one tree, and the leaves of one branch. Verily I say, whatsoever leadeth to the decline of ignorance and the increase of knowledge hath been, and will ever remain, approved in the sight of the Lord of creation. Say: O people! Walk ye neath the shadow of justice and truthfulness and seek ye shelter within the tabernacle of unity.

The preceding word “Say:” emphasizes the point that it is the Voice of God that is speaking.  Again and again in His Revelation, Baha’u’llah emphasizes that what God wants most from humanity in this Day in history is to establish unity, founded on justice and fairness to all peoples, ultimately an expression of love.