When the Visnudutas arrived, they spoke to the Yamadutas with extreme gravity: What are you doing? Stop! You cannot take this man to Yamaraja!

A Vaisnava, one who has surrendered to the lotus feet of Lord Visnu, is always protected by Lord Visnus order-carriers. Because Ajamila had chanted the holy name of Narayana, the Visnudutas not only immediately arrived on the spot but also at once ordered the Yamadutas not to touch him. By speaking with resounding voices, the Visnudutas threatened to punish the Yamadutas if they continued trying to snatch Ajamilas soul from his heart. The order-carriers of Yamaraja have jurisdiction over all sinful living entities, but the messengers of Lord Visnu are capable of punishing anyone, including Yamaraja, if he wrongs a Vaisnava.

Modern scientists do not know where to find the soul within the body with their material instruments, but here the Srimad-Bhagavatam clearly explains that the soul is within the core of the heart (hrdaya); it is from the heart that the Yamadutas were trying to extract the soul of Ajamila. The heart is part of the mechanical arrangement of the body. As the Lord says in the Bhagavad-gita (18.61):

Ones body is created through the agency of maya according to ones activities in ones past life; and according to ones activities in this life, maya creates another body for the next life. At the appropriate time, ones next body is immediately chosen, and both the individual soul and the Supersoul transfer to that particular bodily machine. This is the process of transmigration of the soul.

During transmigration from one body to the next, the sinful soul is taken away by the order-carriers of Yamaraja and put into a particular type of hellish life in order to become accustomed to the condition in which he will live in his next body.