"... man must pass from degree to degree of progressive unfoldment until perfection is attained."

"It is evident, therefore, that man is in need of divine education and inspiration, that the spirit and bounties of God are essential to his development. That is to say, the teachings of Christ and the Prophets are necessary for his education and guidance. Why? Because They are the divine Gardeners Who till the earth of human hearts and minds. They educate man, uproot the weeds, burn the thorns and remodel the waste places into gardens and orchards where fruitful trees grow. The wisdom and purpose of Their training is that man must pass from degree to degree of progressive unfoldment until perfection is attained. For instance, if a man should live his entire life in one city, he cannot gain a knowledge of the whole world. To become perfectly informed he must visit other cities, see the mountains and valleys, cross the rivers and traverse the plains. In other words, without progressive and universal education perfection will not be attained."

`Abdu'l-Bahá, The Promulgation of Universal Peace, p. 295
29 August 1912 - Talk at Home of Madame Morey - Malden, Massachusetts

"... in this world of being, all things must ever be made new."

"Note thou carefully that in this world of being, all things must ever be made new. Look at the material world about thee, see how it hath now been renewed. The thoughts have changed, the ways of life have been revised, the sciences and arts show a new vigour, discoveries and inventions are new, perceptions are new. How then could such a vital power as religion—the guarantor of mankind’s great advances, the very means of attaining everlasting life, the fosterer of infinite excellence, the light of both worlds—not be made new? This would be incompatible with the grace and loving-kindness of the Lord.

Religion, moreover, is not a series of beliefs, a set of customs; religion is the teachings of the Lord God, teachings which constitute the very life of humankind, which urge high thoughts upon the mind, refine the character, and lay the groundwork for man’s everlasting honour."

-`Abdu'l-Bahá, Selections From the Writings of ‘Abdu’l-Bahá, pp. 52-53