We have to maintain our body. This is called bibhrat. That is necessary. We have got this body in this material world. This is not spiritual world. In the spiritual world there is no necessity of maintaining the body. The body is spiritual. As we have got here in this material world, to maintain this body I require to eat, I require to sleep, I require to satisfy my sense, and I require to defend - the four necessities... Ahara-nidra-bhaya-maithunam ca. And spiritual body means these four kinds of bodily demands, nil, no more. That is spiritual life.
Lecture on Srimad-Bhagavatam 6.1.22, Chicago, 6 July, 1975