LoB verse 31
31. The four prominent features of autumn are that there is no water in the sky, the weeds that grew here and there in the rainy season all wither away, the muddy roads and fields dry up, and the ponds of water become crystal clear. These four features of the autumn atmosphere are compared to the four orders of life.
In the varṇāśrama system the student goes to the āśrama of the master to take lessons from him and serve him, even as a menial servant. The troubles o the student are at once mitigated when he attains transcendental knowledge in terms of his relation with Śrī Kṛṣṇa, the Personality of Godhead. As the white clouds no longer bear the burden of water in the autumn sky, the student finds that the troubles of drawing water for the master become a burdenless job if the student, by the grace of his master, attains to spiritual knowledge.
Householders who beget children without restriction, like weeds in the rainy season, become solitary as soon as they attain to the stage of devotional service. The family planning of a godless civilization cannot check weedlike unwanted population. People should learn to check sex life by voluntary restraint. This voluntary restraint is possible when one is dovetailed with the service of the Lord. This is confirmed in Bhagavad-gītā. Well-situated devotees of the Lord refrain from materialistic sense enjoyment, for they are attracted by the beauty of the Transcendence. Forcible restraint by regulative family planning or similar artificial means cannot work very long; one must be attracted by the Transcendence. Once can give up the inferior quality of enjoyment as soon as one receives the superior quality of spiritual enjoyment. So family planning is successful when one is engaged in the culture of the human spirit.
The vānaprasthas, who voluntarily avoid cleaning themselves and who allow their beards and nails to grow, no longer feel the discomforts of these burdens when they engage in the service of the Lord. And above all, the mendicants who take a vow to refrain from sex life no longer feel sexual urges when fixed in the transcendental service of the Lord.
Therefore, in all four spiritual orders and four grades of social life, devotional service to the Lord is essential. Without this relationship, all the regulative principles of varṇa and āśrama become burdensome duties, as they have in the age of Kali. When the regulative principles have no aim, the varṇas become a caste system and the āśramas become the business of various shopkeepers. All these anomalies of the present social system can be reformed only by cultivation of the human spirit in the devotional service of the Lord.