SB 2.7.21

dhanvantariś ca bhagavān svayam eva kīrtir
 nāmnā nṛṇāṁ puru-rujāṁ ruja āśu hanti
yajñe ca bhāgam amṛtāyur-avāvarundha
 āyuṣya-vedam anuśāsty avatīrya loke
Synonyms: 
dhanvantariḥ — the incarnation of God named Dhanvantari; ca — and; bhagavān — the Personality of Godhead; svayam eva — personally Himself; kīrtiḥ — fame personified; nāmnā — by the name; nṛṇām puru-rujām — of the diseased living entities; rujaḥ — diseases; āśu — very soon; hanti — cures; yajñe — in the sacrifice; ca — also; bhāgam — share; amṛta — nectar; āyuḥ — duration of life; ava — from; avarundhe — obtains; āyuṣya — of duration of life; vedam — knowledge; anuśāsti — directs; avatīrya — incarnating; loke — in the universe.
Translation: 
The Lord in His incarnation of Dhanvantari very quickly cures the diseases of the ever-diseased living entities simply by His fame personified, and only because of Him do the demigods achieve long lives. Thus the Personality of Godhead becomes ever glorified. He also exacted a share from the sacrifices, and it is he only who inaugurated the medical science or the knowledge of medicine in the universe.
Purport: 

As stated in the beginning of the Śrīmad-Bhāgavatam, everything emanates from the ultimate source of the Personality of Godhead; it is therefore understood in this verse that medical science or knowledge in medicine was also inaugurated by the Personality of Godhead in His incarnation Dhanvantari, and thus the knowledge is recorded in the Vedas. The Vedas are the source of all knowledge, and thus knowledge in medical science is also there for the perfect cure of the diseases of the living entity. The embodied living entity is diseased by the very construction of his body. The body is the symbol of diseases. The disease may differ from one variety to another, but disease must be there just as there is birth and death for everyone. So, by the grace of the Personality of Godhead, not only are diseases of the body and mind cured, but also the soul is relieved of the constant repetition of birth and death. The name of the Lord is also called bhavauṣadhi, or the source of curing the disease of material existence.