the head corner-stone of the foundation itself

O ye that stand fast in the Covenant! When the hour cometh that this wronged and broken-winged bird will have taken its flight into the Celestial Concourse, when it will have hastened to the Realm of the Unseen and its mortal frame will have been either lost or hidden neath the dust, it is incumbent upon the Afnan, that are steadfast in the Covenant of God and have branched from the Tree of Holiness; the Hands, (pillars) of the Cause of God (the glory of the Lord rest upon them), and all the friends and loved ones, one and all to bestir themselves and arise with heart and soul and in one accord, to diffuse the sweet savors of God, to teach His Cause and to promote His Faith. It behooveth them not to rest for a moment, neither to seek repose. They must disperse themselves in every land, pass by every clime, and travel throughout all regions. Bestirred, without rest, and steadfast to the end, they must raise in every land the triumphal cry "Ya Baha'u'l-Abha!" (O Thou the Glory of Glories), must achieve renown in the world wherever they go, must burn brightly even as a candle in every meeting and must kindle the flame of Divine love in every assembly; that the light of truth may rise resplendent in the midmost heart of the world, that throughout the East and throughout the West a vast concourse may gather under the shadow of the Word of God, that the sweet savors of holiness may be diffused, that faces may shine radiantly, hearts be filled with the Divine spirit and souls be made heavenly.

In these days, the most important of all things is the guidance of the nations and peoples of the world. Teaching the Cause is of utmost importance for it is the head corner-stone of the foundation itself. This wronged servant has spent his days and nights in promoting the Cause and urging the peoples to service. He rested not a moment, till the fame of the Cause of God was noised abroad in the world and the celestial strains from the Abha Kingdom roused the East and the West. The beloved of God must also follow the same example. This is the secret of faithfulness, this is the requirement of servitude to the Threshold of Baha!

~Abdu'l-Baha, The Will and Testament