by Kadamba Kanana Swami
Srila Prabhupada introduced these rules; to fast one month from spinach (sak), one month from yoghurt, one month from milk and one month from urad dahl. This has been the standard in ISKCON temples during his presence and also for quite a number of years after his departure. However gradually this practice is not so widely followed anymore, although it continues to be mentioned on the vaisnava calendar.
Caitanya Caritamrta, Madhya 4.169
grisma-kala-ante punah nilacale gela
nilacale caturmasya anande rahila
TRANSLATION
At the end of summer Madhavendra Puri returned to Jagannatha Puri, where he remained with great pleasure during the whole period of Caturmasya.PURPORT
The Caturmasya period begins in the month of Asadha (June-July) from the day of Ekadasi called Sayana-ekadasi in the fortnight of the waxing moon. The period ends in the month of Kartika (October-November) on the Ekadasi day known as Utthana-ekadasi in the fortnight of the waxing moon. This four-month period is known as Caturmasya. Some Vaisnavas also observe it from the full-moon day of Asadha until the full-moon day of Kartika. That is also a period of four months. This period, caiculated by the lunar months, is called Caturmasya, but others also observe Caturmasya according to the solar month from Sravana to Kartika. The whole period, either lunar or solar, takes place during the rainy season. Caturmasya should be observed by all sections of the population. it does not matter whether one is a grhastha or a sannyasi. The observance is obligatory for all asramas. The real purpose behind the vow taken during these four months is to minimize the quantity of sense gratification. This is not very difficult. In the month of Sravana, one should not eat spinach. In the month of Bhadra, one should not eat yogurt, and in the month of Asvina, one should not drink milk. One should not eat fish or other nonvegetarian food during the month of Kartika. A nonvegetarian diet means fish and meat. Similarly, masura dahl and urad dahl are also considered nonvegetar an. These two dahls contain a great amount of protein, and food rich in protein is considered nonvegetarian. On the whole, during the four-month period of Caturmasya, one should practice giving up all food intended for sense enjoyment.
I think this is a clear instruction from Srila Prabhupada, if we follow it we will get his blessings, which is most desirable.It will be very nice if we can call ourselves faithful followers of Srila Prabhupada.
"He lives forever and the follower lives with him."
I think it should be followed, except when health reasons dictate otherwise. Especially milk can be difficult to replace.
It is true that I would be happy if my disciples could follow this. I have also always followed this except during times when I had major health problems.
Additionally during the month of Kartika we may add a vow and for one month for example to especially increase our hearing and chanting and sometimes minimize our eating to help develop more sense control. As a warning I would like to add, that we should not take such a vow lightly, when we take it we are meant to follow it. So we must be a little careful not to make our vows to difficult, for example a quota of rounds that may be more than we can practically complete. Also I have seen some people taking to a rigid fast putting the emphasis more on performing austerity and too little on the real essence of hearing and chanting. One should not tell others about the vows one is performing, especially not before they are completed, because we may come under the influence of false prestige, which would spoil the whole thing.
Sometimes devotees also take other additional vows, I remember that Bhurijana prabhu in Vrndavan one year took a vow, not to say anything critical about any vaisnava. A very nice... and very difficult vow indeed.
The last five days of Kartika are known as Bhisma Pancaka, one can also take a vow for just these five days or when we have the time and opportunity we can intensify the kartika vow we had already taken.
By performing such vows of Caturmasya one can quickly make more and more advancement in spiritual life.
The restrictions for the four months; first month no spinach, second month no yoghurt, third no milk and fourth no urad dahl are meant to be followed by all asramas. Kartika vratas and additionally Bhisma Pancaka are optional and it depends on ones personal situation if they are followed or not. If we are very busy with practical work, it may become too much of a burden to add extra austerities or we may not manage to increase our hearing and chanting. However if we can do something then following such optional vows for the pleasure of Krsna can be very favorable.