strive for spiritual capacity

"Sterile soil will produce nothing, even if the cloud of mercy pours rain upon it a thousand years. We must make the soil of our hearts receptive and fertile by tilling in order that the rain of divine mercy may refresh them

and bring forth roses and hyacinths of heavenly planting. 

We must have perceiving eyes in order to see the light of the sun. We must cleanse the nostril in order to scent the fragrances of the divine rose garden. We must render the ears attentive in order to hear the summons of the supreme Kingdom. 

No matter how beautiful the melody, the ear that is deaf cannot hear it, cannot receive the call of the Supreme Concourse. The nostril that is clogged with dust cannot inhale the fragrant odors of the blossoms. 

Therefore, we must ever strive for capacity and seek readiness. As long as we lack susceptibility, the beauties and bounties of God cannot penetrate. Christ spoke a parable in which He said His words were like the seeds of the sower; some fall upon stony ground, some upon sterile soil, some are choked by thorns and thistles, but some fall upon the ready, receptive and fertile ground of human hearts."

(Abdu'l-Baha, The Promulgation of Universal Peace, p. 148)