"So it's final, From now on we will be friends. Meet me tomorrow, I will introduce you to our group. You are going to like them."
Karna stretched his hands towards Ashwatthama to finalise their friendship. Now he doesn't have to worry about any unexpected things because once a word is given in this time, Most people rather lose their heads then to fail to keep their word.
Even the Niyati will can't do anything to force them to turn from their words as these peoples are very strong-willed. Some people literally lost their heads just to keep their word. That too an Asura who conquered both heaven and earth.
So Karna is not too worried, Of course, there is tiny doubt but that is given as you can't be too careful against destiny, Who knows what game it will play to let things happen as they are supposed to.
"Hum, We are now friends, Mohod- Mitra, I will love to meet them, Hope they will like me."