Theory:

“Forgive me!” said the bearded man in a weak voice when he saw that the king was awake.
 
“I do not know you and have nothing to forgive you for,” said the king.

“You do not know me, but I know you. I am that enemy of yours who swore revenge on you, because you put my brother to death and seized my property. I knew you had gone alone to see that hermit, and I made up my mind to kill you on your way home. But the day passed and you did not return. So I left my hiding-place, and I came upon your bodyguard, who recognised me and wounded me. I escaped from him but I should have died if you had not dressed my wounds. I wished to kill you, and you have saved  my life. Now, if I live, I will serve you as your most faithful servant and will order my sons to do the same. Forgive me!” 
 Explanation:
  
The bearded man asked the king to forgive him, in a weak voice - as soon as the king awoke.
 
The king said that he doesn't know him and he has nothing to forgive him.
 
The bearded man started explaining how he knew the king. He said the king might not know him, but he knew the king. He also confessed that he was an enemy of the king, who had come to kill him. He explained that the king had killed his brother and took his property. He revealed his plan to kill the king because he came to know that he had gone alone to meet the hermit. He also says that he waited in a hiding place for the king to return, but since he did not return, he came out. That was when the bodyguard recognized him and wounded him. He continued, it was finally the king himself who dressed his wound and saved his life. The bearded man felt bad that he had come to kill the king, but the king had saved his life. So he wished and asked the king to let him be his faithful servant and promised that he would order his sons to do the same.
  
Meanings of difficult words:
  
Word
Meaning
Swore revengeTo hurt someone in return for being hurt by that person.
SeizedTook by force.
Reference:
 
National Council of Educational Research and Training (2007). Honeycomb. Three Questions - Leo Tolstoy (pp. 7-13). Published at the Publication Division
by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.