SB 7.12.24
atmany agnin samaropya
sannyasyaham mamatmatam
karanesu nyaset samyak
sanghatam tu yatharhatah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
He should properly place the fire element in his own self and in this way give up bodily affinity, by which one thinks the body to be one’s self or one’s own. One should gradually merge the material body into the five elements [earth, water, fire, air and sky].
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The body is an effect of a cause, namely the five material elements (earth, water, fire, air and sky). In other words, one should know perfectly well that the material body is nothing but a combination of the five elements. This knowledge constitutes merging of the material body and the five material elements. Merging into Brahman in perfect knowledge means understanding perfectly that one is not the body but a spiritual soul.