Both Bahá’u’lláh and the Bab emphasize the need of children in marriage. The latter, for example, states that to beget children is the highest physical fruit of man’s existence.
(Shoghi Effendi, Unrestrained as the Wind, p. 132)
One who performeth neither good deeds nor acts of worship is like unto a tree which beareth no fruit, and an action which leaveth no trace. Whosoever experienceth the holy ecstasy of worship will refuse to barter such an act or any praise of God for all that existeth in the world.
(Bahá’u’lláh, The Importance of Obligatory Prayer and Fasting)
The Tree of Life is full of blossoms, leaves and fruits!—shade thereof is a peace to the soul and a rest to the consciousness. Whosoever is under this Tree will certainly partake of fruit. But shade trees are many in the forest, which, though fresh and verdant, are, nevertheless, fruitless. This truth shall finally become clear and manifest unto thee.
(‘Abdu’l-Bahá, Tablets of ‘Abdu’l-Bahá v1, p. 126)
The basest of men are they that yield no fruit on earth. Such men are verily counted as among the dead, nay better are the dead in the sight of God than those idle and worthless souls.
(Bahá’u’lláh, The Persian Hidden Words #81)
The fleeting hours of man’s life on earth pass swiftly by and the little that still remaineth shall come to an end, but that which endureth and lasteth for evermore is the fruit that man reapeth from his servitude at the Divine Threshold.
(‘Abdu’l-Bahá, Selections from the Writings of ‘Abdu’l-Bahá, p. 234)
There are many things which will, if neglected, be wasted, and come to nothing. How often in this world do we see a child who has lost his parents and who, unless attention be devoted to his education and training, can produce no fruit. And better off dead than alive is he who produceth no fruit.
(Bahá’u’lláh, The Compilation of Compilations vol. I, p. 247)
What are the fruits of the human world? They are the spiritual attributes which appear in man. If man is bereft of those attributes, he is like a fruitless tree. One whose aspiration is lofty and who has developed self-reliance will not be content with a mere animal existence. He will seek the divine Kingdom; he will long to be in heaven although he still walks the earth in his material body, and though his outer visage be physical, his face of inner reflection will become spiritual and heavenly. Until this station is attained by man, his life will be utterly devoid of real outcomes. The span of his existence will pass away in eating, drinking and sleeping, without eternal fruits, heavenly traces or illumination—without spiritual potency, everlasting life or the lofty attainments intended for him during his pilgrimage through the human world. You must thank God that your efforts are high and noble, that your endeavors are worthy, that your intentions are centered upon the Kingdom of God and that your supreme desire is the acquisition of eternal virtues. You must act in accordance with these requirements. A man may be a Bahá’í in name only. If he is a Bahá’í in reality, his deeds and actions will be decisive proofs of it. What are the requirements? Love for mankind, sincerity toward all, reflecting the oneness of the world of humanity, philanthropy, becoming enkindled with the fire of the love of God, attainment to the knowledge of God and that which is conducive to human welfare.
(‘Abdu’l-Bahá, The Promulgation of Universal Peace, p. 335)
… the fruit of man’s earthly existence, which is the recognition of the one true God …
(Bahá’u’lláh, Gleanings from the Writings of Bahá’u’lláh, p. 344-345)