Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 46

Sanskrit:

गावो मृगा: खगा नार्य: पुष्पिण्य: शरदाभवन् ।अन्वीयमाना: स्ववृषै: फलैरीशक्रिया इव ॥ ४६ ॥

ITRANS:

gāvo mṛgāḥ khagā nāryaḥpuṣpiṇyaḥ śaradābhavananvīyamānāḥ sva-vṛṣaiḥphalair īśa-kriyā iva

Translation:

By the influence of the autumn season, all the cows, doe, women and female birds became fertile and were followed by their respective mates in search of sexual enjoyment, just as activities performed for the service of the Supreme Lord are automatically followed by all beneficial results.

Purport:

Śrīla Prabhupāda comments, “On the arrival of the autumn season, all the cows, deer, birds and females in general become pregnant, because in that season generally all the husbands become impelled by sex desire. This is exactly like the transcendentalists who, by the grace of the Supreme Lord, are bestowed with the benediction of their destinations in life. Śrīla Rūpa Gosvāmī has instructed in his Upadeśāmṛta that one should perform devotional service with great enthusiasm, patience and conviction and should follow the rules and regulations, keep oneself clean from material contamination and stay in the association of devotees. By following these principles, one is sure to achieve the desired result of devotional service. For he who patiently follows the regulative principles of devotional service, the time will come when he will achieve the result, as the wives who reap results by becoming pregnant.”