Cāturmāsya should be observed by all sections of the population. It does not matter whether one is a gṛhastha or a sannyāsī. The observance is obligatory for all āśramas. 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 Śrāvaṇa one should not eat spinach, in the month of Bhādra one should not eat yogurt, and in the month of Āśvina one should not drink milk. One should not eat fish or other nonvegetarian food during the month of Kārttika. A nonvegetarian diet means fish and meat. Similarly, masūra dhal and urad dhal are also considered nonvegetarian. These two dhals contain a great amount of protein, and food rich in protein is considered nonvegetarian. On the whole, during the four-month period of Cāturmāsya one should practice giving up all food intended for sense enjoyment.
(SRI CAITANYA CARITAMRTA------2:4:169-----PURPORT).