Duty to Work:
It is incumbent upon each one of you to engage in some occupation – such as a craft, a trade or the like. We have exalted your engagement in such work to the rank of worship of the one true God. Reflect, O people, on the grace and blessings of your Lord, and yield Him thanks at eventide and dawn. Waste not your hours in idleness and sloth, but occupy yourselves with what will profit you and others. Thus hath it been decreed in this Tablet from whose horizon hath shone the day-star of wisdom and utterance. The most despised of men in the sight of God are they who sit and beg.
(Baha’u’llah: The Kitab-i-Aqdas, p. 30)

Please God, the poor may exert themselves and strive to earn the means of livelihood. This is a duty which, in this most great Revelation, hath been prescribed unto every one, and is accounted in the sight of God as a goodly deed. Whoso observeth this duty, the help of the invisible One shall most certainly aid him.
(Baha’u’llah: Gleanings, p. 202)

Thus it is incumbent on every one to engage in crafts and professions, for therein lies the secret of wealth, O men of understanding! For results depend upon means, and the grace of God shall be all-sufficient unto you.
(Baha’u’llah: Persian Hidden Words, p. 80)

It is the duty of those who are in charge of the organization of society to give every individual the opportunity of acquiring the necessary talent in some kind of profession, and also the means of utilizing such a talent, both for its own sake and for the sake of earning the means of his livelihood. Every individual, no matter how handicapped and limited he may be, is under the obligation of engaging in some work or profession, for work, especially when performed in the spirit of service, is according to Baha’u’llah a form of worship. It has not only a utilitarian purpose, but has a value in itself, because it draws us nearer to God, and enables us to better grasp His purpose for us in this world.
(Shoghi Effendi, quoted by the Universal House of Justice: Aqdas: Notes, p. 192)

Work is Worship:
In the Baha’i Cause arts, sciences and all crafts are (counted as) worship. The man who makes a piece of notepaper to the best of his ability, conscientiously, concentrating all his forces on perfecting it, is giving praise to God. Briefly, all effort and exertion put forth by man from the fullness of his heart is worship, if it is prompted by the highest motives and the will to do service to humanity. This is worship: to serve mankind and to minister to the needs of the people. Service is prayer. A physician ministering to the sick, gently, tenderly, free from prejudice and believing in the solidarity of the human race, he is giving praise.
(`Abdu’l-Baha: Paris Talks, pp. 176-177)

In this great dispensation, art (or a profession) is identical with an act of worship and this is a clear text of the Blessed Perfection. Therefore, extreme effort should be made in art and this will not prevent the teaching of the people in that region. Nay, rather, each should assist the other in art and guidance.
(`Abdu’l-Baha: Baha’i World Faith, p. 377)

Service to Humanity:
Man’s merit lieth in service and virtue and not in the pageantry of wealth and riches.
(Baha’u’llah: Tablets of Baha’u’llah, p. 138)

That one indeed is a man who, today, dedicateth himself to the service of the entire human race.
(Baha’u’llah: Gleanings, p. 250)

The tie of servitude established between the worshiper and the adored One, between the creature and the Creator, should in itself be regarded as a token of His gracious favor unto men, and not as an indication of any merit they may possess.
(Baha’u’llah: Gleanings, pp. 193-194)

Therefore, order your lives in accordance with the first principle of the divine teaching, which is love. Service to humanity is service to God.
(`Abdu’l-Baha: Promulgation of Universal Peace, p.8)

You must consider all His servants as your own family and relations. Direct your whole effort toward the happiness of those who are despondent, bestow food upon the hungry, clothe the needy, and glorify the humble. Be a helper to every helpless one, and manifest kindness to your fellow creatures in order that ye may attain the good pleasure of God. This is conducive to the illumination of the world of humanity and eternal felicity for yourselves.
(`Abdu’l-Baha: Promulgation of Universal Peace, p. 469)

Think ye at all times of rendering some service to every member of the human race. Pay ye no heed to aversion and rejection, to disdain, hostility, injustice: act ye in the opposite way. Be ye sincerely kind, not in appearance only. Let each one of God’s loved ones centre his attention on this: to be the Lord’s mercy to man; to be the Lord’s grace. Let him do some good to every person whose path he crosseth, and be of some benefit to him. Let him improve the character of each and all, and reorient the minds of men.
(`Abdu’l-Baha: Selections … `Abdu’l-Baha, p. 3)

Again, is there any deed in the world that would be nobler than service to the common good? Is there any greater blessing conceivable for a man, than that he should become the cause of the education, the development, the prosperity and honor of his fellow-creatures? No, by the Lord God! The highest righteousness of all is for blessed souls to take hold of the hands of the helpless and deliver them out of their ignorance and abasement and poverty, and with pure motives, and only for the sake of God, to arise and energetically devote themselves to the service of the masses, forgetting their own worldly advantage and working only to serve the general good. “They prefer them before themselves, though poverty be their own lot.”(1) “The best of men are those who serve the people; the worst of men are those who harm the people.”
(`Abdu’l-Baha: Secret of Divine Civilization, p. 103)

1. Qur’an 59:9.