Of course it burnt him from up within.
But this was something he knew that had to be done.
"Even that which is most foul turns pure when submitted to fire," he'd been instructed by his acharya. "Light the fire of knowledge within you and there will be no power in this world which will be able to stop you."
The words reverberated in his mind as he started the yagya in the middle of the forest. He was hypnotized just looking at the flames that danced in the ceremonial pit. The flames seemed to have a life of it's own.
At first, they depended on the ghee and the logs of wood which he'd placed in the pit to establish their presence in this world. The flames seemed to gratifyingly acknowledge that it's own existence wouldn't have been possible without the support provided by the logs of wood.
And slowly, the flames arose and with it came the crackling sound of the wood being burnt. The flames looked at the world with the same power with which a vanquishing army rushes towards the enemy ranks it must clash with on a battle-field.
The warrior paused. He had been watching the flames in a trance, with a fixed stare, an expression-less face and lips firmly pressed together.
Something had stirred within him.
"The fire has been lit, acharya."
A slight smile dancing on his lips, he folded both his hands and bowed reverentially to Agni Dev.