“The real purpose behind the vow taken during these four months is to minimize the quantity of sense gratification. This is not very difficult.”-  Caitanya-caritamrita, Madhya Lila 4.169, Purport 

In the purport to Sri Caitanya-caritamrita, Madhya-lila 4.169, Srila Prabhupada writes that “the Caturmasya period begins in the month of Ashadha (June-July) from the day of Ekadasi called Sayana-ekadasi. The period ends in the month of Kartika (October-November) on the Ekadasi day known as Utthana-ekadasi. This four month period is known as Caturmasya.” In the Sri Hari-bhakti-vilasait is recommended that for the first month of Caturmasya, which is known as Sravana (July–August), one should give up eating any green, leafy vegetables. This includes but is not limited to all types of spinach, coriander, curry leaves, basil and other herbs. In the second month known as Bhadrapada (August –September), one should avoid eating yogurt. For the third month, Asvina (September –October), it is recommended that one should abstain from milk. In the last month, Kartika (October –November), one should not eat white lentils (masura and urad dhals). 

In the Varaha Purana, it describes the significance and origin of the Caturmasya period. Once Mother Earth approached Lord Varaha, the boar incarnation of the Lord, and expressed her concerns about the people who take birth in Kali Yuga. She pointed out how these people are ignorant, short-lived and always afflicted with weakness and disease, and she begged the Lord to reveal a method which would allow the people of Kali Yuga to get great benefits with very little effort. 

Seeing her concern, Lord Varaha smiled and explained that the auspicious four month period of Caturmasya gives many benefits to a person who performs any sort of austerity. Whether it is doing a fire sacrifice, offering charity, or simply chanting the holy names of the Lord, the benefits of performing such an endeavour during Caturmasya are countless. Performing such activities during Caturmasya results in even greater benefit than observing the same austerities during other months of the year.

Lord Varaha continued to explain that these four months are the resting and rising times of the demigods and of the Supreme Creator. He recalled that once He was sitting on the top of Mount Meru when the celestials approached Him and pardoned themselves for the night. Just as they were about to retire for the night, a dark complexioned lady, adorned with sparkling white cloth and holding a battle axe in her hand, approached the Lord and prostrated herself before Him.   

After offering suitable prayers to the Lord she identified herself as Ratri, the overseer of this part of the year. She expressed her anguish at being termed as an inauspicious time of the year. Since the Supreme Lord and the demigods take rest during her four months, auspicious activities such as marriages aren’t performed. Having lost her will to live because of this, she begged the Lord to show some mercy towards her. Hearing her plea, the assembled demigods prayed to the Lord, asking Him to kindly bestow mercy upon Ratri. 

Being pleased with the prayers of the demigods, Lord Varaha granted a boon to Ratri Devi. He said, “Oh Ratri, you have three yamas(1 yama is 2 months). Out of these three yamasthe first two yamaswill henceforth become dear to me. Any pious deed performed during these two yamasbrings forth immense merits. Among these four months of Sravana, Bhadrapada, Asvina, and Kartika the merits accrued will increase day by day. That is the reason why the last month, Kartika, is most beneficial in all respects.” Upon receiving this boon, Ratri Devi became pacified and happily returned to her abode.  

Lord Varaha concluded by explaining to Bhumi Devi that from that time onward, He benevolently grants great merits to one who performs pious activities and austerities. Hearing this, Mother Earth felt peaceful. 

In the Sri Hari-bhakti-vilasa, the observation of Caturmasya is explicitly described. There are various observances, which if strictly followed will amount to great merit. For example, if one rests on the ground or on stone, they become an associate of Lord Visnu, or if one refrains from speaking nonsense, prajalpa, one’s order will never be disobeyed.There are many such observances that can be performed. If one follows any of these relatively simple vratas, the benefits received from such an austerity greatly outweigh the austerities endured, thus giving the people in the age of Kali a chance to obtain great merit and advancement. 

It is stated in the "Нектаре преданности"that by following the regulative principles of Caturmasya, one can quickly be raised to the platform of devotional service. The observation of Caturmasya is meant to increase one’s devotion to Lord Krishna and to decrease sense gratification, so whatever is done during Caturmasya should support one’ssadhanaand service, and should not inhibit it.The four month period of Caturmasya is an opportunity for devotees and non-devotees alike to reap immense spiritual benefit from the performance of the simplest of austerities to the best of one’s ability. It is the quality of one’s vratarather than the quantity that is most pleasing to Krishna, and so any effort made for the pleasure of the Lord is greatly appreciated and well rewarding. 

In a purport in the Sri Caitantya-caritamrita, Srila Prabhupada explains how the observation of Caturmasya is obligatory for those in all ashramas. He emphasises this as an opportunity for people to reduce their amount of sense gratification – this is the real purpose behind the observation of Caturmasya. The basic observance of avoiding leafy greens, yogurt, milk, masuraи urad dhals and increasing one’s sadhanais sufficient for one to obtain limitless mercy from the Lord– such is the mercy of the Supreme Personality of Godhead.