The Supreme Lord is situated in everyones heart, O Arjuna, and is directing the wanderings of all living entities, who are seated as on a machine, made of the material energy. The living entity, who is part and parcel of the Supreme Personality of Godhead, exists on the mercy of the Lord, who is always with him in any form of body. The living entity desires a particular type of material enjoyment, and thus the Lord supplies him with a body, which is like a machine. Just to keep him alive in that body, the Lord remains with him as the purusa (Ksirodakasayi Visnu). This is also confirmed in Brahma-samhita (5.35):

I worship the Personality of Godhead, Govinda, who enters the existence of every universe and every atom by one of His plenary portions and thus manifests His infinite energy throughout the material creation. The living entity, being part and parcel of the Lord, is known as jiva. The Supreme Lord purusa remains with the jiva to enable him to enjoy material facilities.