…The National Fund must be firmly established, generously supported and universally and continuously upheld, for it is the prerequisite of future progress and achievement.
(Shoghi Effendi: Funds, p. 532)

And as the progress and execution of spiritual activities is dependent and conditioned upon material means, it is of absolute necessity that immediately after the establishment of local as well as national Spiritual Assemblies, a Baha’i Fund be established, to be placed under the exclusive control of the Spiritual Assembly. All donations and contributions should be offered to the Treasurer of the Assembly, for the express purpose of promoting the interests of the Cause, throughout that locality or country. It is the sacred obligation of every conscientious and faithful servant of Baha’u’llah who desires to see His Cause advance, to contribute freely and generously for the increase of that Fund. The members of the Spiritual Assembly will at their own discretion expend it to promote the Teaching Campaign, to help the needy, to establish educational Baha’i institutions, to extend in every way possible their sphere of service. I cherish the hope that all the friends, realizing the necessity of this measure, will bestir themselves and contribute, however modestly at first, towards the speedy establishment and the increase of that Fund.
(Shoghi Effendi: Baha’i Administration, pp. 41-42)

Only Baha’is May Contribute:
…He [Shoghi Effendi] wishes me to stress again that under no circumstances the believers should accept any financial help from non-Baha’is for use in connection with specific administrative activities of the Faith such as the Temple construction fund, and other local or national Baha’i administrative funds. The reason for this is twofold: First because the institutions which the Baha’is are gradually building are in the nature of gifts from Baha’u’llah to the world; and secondly the acceptance of funds from non-believers for specific Baha’i use would, sooner or later, involve the Baha’is into unforeseen complications and difficulties with others, and thus cause incalculable harm to the body of the Cause.
(Shoghi Effendi: Lights of Guidance, pp. 254-255)

One of the distinguishing features of the Cause of God is its principle of non-acceptance of financial contributions for its own purposes from non-Baha’is: support of the Baha’i Fund is a bounty reserved by Baha’u’llah to His declared followers. This bounty imposes full responsibility for financial support of the Faith on the believers alone, every one of whom is called upon to do his utmost to ensure that the constant and liberal outpouring of means is maintained and increased to meet the growing needs of the Cause.
(The Universal House of Justice: Lights of Guidance, pp. 251-252)

The crucial point in deciding whether or not funds may be accepted from non-Baha’i sources is the purpose for which the funds are to be used. As you know, it is absolutely forbidden in the Faith to accept from non-Baha’is contributions towards the work of the Cause itself. However, in addition to the work of spreading the Faith and establishing its institutions, Spiritual Assemblies also engage in humanitarian activities, and contributions from non-Baha’i sources may be accepted towards such activities. Indeed, although we never ask individual non-Baha’is for funds, it sometimes happens that a person who has a great admiration for the Faith insists on contributing. In such a case the contribution may be accepted, with the express provision that it will be used only for charitable and humanitarian purposes.
(The Universal House of Justice: Lights of Guidance, p. 255)

Giving is a Responsibility, Privilege, and Bounty:
In brief, O ye friends of God, rest assured that in place of this contribution, your commerce, your agriculture and industries shall be blessed many times….
(`Abdu’l-Baha: Lights of Guidance, p. 251)

…our contributions to the Faith are the surest way of lifting once and for all time the burden of hunger and misery from mankind, for it is only through the system of Baha’u’llah – Divine in origin – that the world can be gotten on its feet and want, fear, hunger, war, etc., be eliminated. Non-Baha’is cannot contribute to our work or do it for us; so really our first obligation is to support our own teaching work, as this will lead to the healing of the nations.
(Shoghi Effendi: Lights of Guidance, p. 122)

We must be like the fountain or spring that is continually emptying itself of all that it has and is continually being refilled from an invisible source. To be continually giving out for the good of our fellows undeterred by fear of poverty and reliant on the unfailing bounty of the Source of all wealth and all good – this is the secret of right living.
(Shoghi Effendi: Directives of the Guardian, p. 32)

…all contributions to the Fund are to be purely and strictly voluntary in character. It should be made clear and evident to every one that any form of compulsion, however slight and indirect, strikes at the very root of the principle underlying the formation of the Fund ever since its inception. While appeals of a general character, carefully worded and moving and dignified in tone are welcome under all circumstances, it should be left entirely to the discretion of every conscientious believer to decide upon the nature, the amount, and purpose of his or her contribution for the propagation of the Cause.
(Shoghi Effendi: Baha’i Administration, p. 101)

Giving to the Fund, therefore, is a spiritual privilege, not open to those who have not accepted Baha’u’llah, of which no believer should deny himself. It is both a responsibility and a source of bounty. This is an aspect of the Cause which, we feel, is an essential part of the basic teaching and deepening of new believers. The importance of contributing resides in the degree of sacrifice of the giver, the spirit of devotion with which the contribution is made and the unity of the friends in this service; these attract the confirmations of God and enhance the dignity and self-respect of the individuals and the community.
(The Universal House of Justice: Lights of Guidance, p. 252)

There is a profound aspect to the relationship between a believer and the Fund, which holds true irrespective of his or her economic condition. When a human soul accepts Baha’u’llah as the Manifestation of God for this age and enters into the divine Covenant, that soul should progressively bring his or her whole life into harmony with the divine purpose – he becomes a co-worker in the Cause of God and receives the bounty of being permitted to devote his material possessions, no matter how meagre, to the work of the Faith.
(The Universal House of Justice: Lights of Guidance, p. 252)

Expenditure of Funds:
The financial questions that confront the Cause are all very pressing and important. They need a judicious administration and wise policy. We should study the needs of the Cause, find which field will give the greatest yield, and then appropriate the necessary funds. And such a task is surely most difficult and responsible.
(Shoghi Effendi: Funds, p. 545)

It should therefore be the aim of every local and national community to become not only self-supporting, but to expend its funds with such wisdom and economy as to be able to contribute substantially to the Baha’i International Fund, thus enabling the House of Justice to aid the work in fruitful but impoverished areas, to assist new National Assemblies to start their work, to contribute to major international undertakings….
(The Universal House of Justice: Lights of Guidance, p. 251)