Bahá’í Sacred Writings, Bahá’u’lláh, #117

Strain every nerve to acquire both inner and outer perfections, for the fruit of the human tree hath ever been and will ever be perfections both within and without. It is not desirable that a man be left without knowledge or skills, for he is then but a barren tree. Then, so much as capacity and capability allow, ye needs must deck the tree of being with fruits such as knowledge, wisdom, spiritual perception, and eloquent speech.