To be brief, it hath been decided by the Desire of God that union and harmony may day by day increase among the friends of God and the maid-servants of the Merciful One, in the West. Not until this is realized will the affairs advance by any means whatever! And the greatest means for the union and harmony of all is Spiritual Meetings. This matter is very important and is as a magnet (to attract or) for divine confirmation.
(‘Abdu’l-Bahá, Tablets of ‘Abdu’l-Bahá v1, p. 124-125)