Prophecies regarding the House of Worship

The hearts will be dilated, and the people will stand firm in the Cause

"You will soon see the angels of confirmation following after you and the hosts of reinforcement crowding before you."

"When the Mashriqu'l-Adhkar is accomplished, when the lights are emanating therefrom, the righteous ones are presenting themselves therein, the prayers are performed with supplication towards the mysterious Kingdom, the voice of glorification is raised to the Lord, the Supreme, then the believers shall rejoice, the hearts shall be dilated and overflow with the love of the All-living and Self-existent God. The people shall hasten to worship in that heavenly Temple, the fragrances of God will be elevated, the divine teachings will be established in the hearts like the establishment of the Spirit in mankind; the people will then stand firm in the Cause of your Lord, the Merciful. Praise and greetings be upon you."

('Abdu'l-Bahá, Bahá'í World Faith, p. 415)

To be a rejoicing of the Concourse on High

The next one is by Abdu'l-Baha, addressed to the Spiritual Assembly of Bushruiyh which roughly says:

Mashriqu'l-Adhkar is the dawning place of the lights and meeting place of the pure. When the precious friends come together in those holy gatherings and commence Obligatory Prayers (namaz), and with wondrous voices (alhan) chant the verses and song the prayers (munajat), the Concourse on High will hear them and cry out: O rejoice and hail! Praise be God that in the nether world, some of the angelic souls of the Abha Kingdom have arisen to prayer and supplication and in a sacred gathering are chanting verses.

("rough translation" at https://bahai-library.com/compilation_mashriq_adhkar_mcglinn )

The Mashriqu'l-Adhkár is to gladden and refresh

In beloved Abdu'l-Baha's Tablet to Mashhadi Abdu'r-Razzaq-i Qumi (pages of 231-2 of Ganjinih Hudud va Ahkam), we find the following (very tentative translation):

The Mashriqu'l-Adhkar is a magnet for attracting divine confirmations. The Mashriqu'l-Adhkar is the great foundation of the forgiving Lord. The Mashriqu'l-Adhkar is the mighty pillar of the religion of the Creator. The establishment of the Mashriqu'l-Adhkar will raise the Word of God. The laudation and praise of God in the Mashriqu'l-Adhkar will gladden the heart of every pious one. The holy fragrance of the Mashriqu'l-Adhkar will uplift every righteous one. The life-giving breeze of the Mashriqu'l-Adhkar will resuscitate all freemen. The effulgence of the Mashriqu'l-Adhkar will light the horizons like the morning sun. The melody of the Mashriqu'l-Adhkar will cheer the spirits of the Concourse on High. The chanting of the verses of unity in the Mashriqu'l-Adhkar will bring joy to the denizens of the Abha Kingdom. In this day, the most important of all undertakings and the end of all services before the holy threshold is the establishment of the Mashriqu'l-Adhkar.

("rough translation" at https://bahai-library.com/compilation_mashriq_adhkar_mcglinn )

Soon to be established in America (and entry be troops with "great enthusiasm and attraction")

... a Mashrak-el-Azcar will soon be established in America. The cries of supplication and invocation will be raised to the Highest Kingdom therefrom and, verily, the people will enter into the religion of God by troops with great enthusiasm and attraction.

(Tablets of 'Abdu'l-Bahá Abbas p. 681)

From North American House of Worship to be "thousands of Mashriqu'l-Adhkars" born (and its "spirit of teaching" to "permeate to all parts of the world")

"A most wonderful and thrilling motion will appear in the world of existence," are Abdu'l-Baha's own words, predicting the release of spiritual forces that must accompany the completion of this most hallowed House of Worship. "From that point of light," He, further glorifying that edifice, has written, "the spirit of teaching ... will permeate to all parts of the world." And again: "Out of this Mashriqu'l-Adhkar, without doubt, thousands of Mashriqu'l-Adhkars will be born." "It marks the inception of the Kingdom of God on earth."

"Again I repeat - and I cannot overrate the vital, the unique importance of the campaign now launched to insure the completion of such an edifice - the immediate destiny of the American Baha'i Community is intimately and inescapably bound up with the outcome of this newly launched, this severely trying, soul-purging, spiritually uplifting campaign.

(Shoghi Effendi, Citadel of Faith, p. 69)

Will, God willing, be Temples of great beauty in all the States of America (especially New York)

"God willing, in all the states of America in the future there will be erected Temples with infinite architectural beauty, art, with pleasing proportion and handsome and attractive appearances; especially in New York. But for the present, be ye satisfied with a rented place."

(Tablets of 'Abdu'l-Bahá Abbas, p. 437)

Poetry to be Recited (but must only consist of verses of God?)

O thou who art attracted by the Fragrances of God!

Verily, I chanted thy poem. Its significance was beautiful, its composition eloquent and its words excellent. It was like the melody of the birds of holiness in the paradise of El-ABHA. The breasts of the maid-servants of the Merciful were exhilarated by its chanting. Blessed art thou for uttering forth such an excellent poem and brilliant pearl.

Verily, these verses shall be sung in the divine meetings and in the assemblages of the spiritual in the course of ages and centuries to come, for thou hast uttered the praise of thy Lord and expressed significant meanings in eulogy of thy Lord, the Merciful, the Clement.

All poems shall be forgotten in the course of time save those that are extraordinary; thy poem shall be chanted with melody and best voices in the Center of Worship (or Mashrak-el-Azcar) forevermore.

(Tablets of 'Abdu'l-Bahá, pp. 57-58)