This is a play of six scenes called as "Veni Samhaara" (Binding-up of the braided hair) written by BhattaNarayana.
While discussing about whom to take as SenaPati or Chief Commander:
Duryodhana told Kripaacharya that Karna is already chosen as SenaPati, so Ashvatthama cannot be chosen.
Then Ashvatthama got little sad and Karna said to him-
Sad people should cry and angry people should take up weapons.
So Ashvatthama got angry and said-
You tell me to cry because I am said. I am not like you who will forget about Shastra-Vidya(knowledge of weapons) because of your Guru's Shaapa(curse). I am from family of warriors and you are son of a weaver.
Then Karna angrily said-
I did not leave the weapon from my hand unlike your father who left the weapons in fear of Dhristadyumna.
And also listen,
सूतो वा सूतपुत्रो वा यो वा को वा भवाम्यहम् ।
दैवायत्तं कुले जन्म मदायत्तं तु पौरुषम् ॥
Whether I am a weaver or whether I am son of a weaver, whoever or whatever I am, this birth in lineage of a family is given by Daiva or Fate. But the Prowess and Power I have accomplished by My Own Self.
Third Scene, VeniSanhaara