I had a servant who ran away form my home because he was bored and wanted some change(not because I was harsh to him).
I called him and said that take your salary for the time that you worked for me. He said I don’t need it. Now after 5 years he has contacted but still did not ask for salary. Am I still bound to give him his salary?

Salary is his right, As you mentioned he worked for you. If again he has contacted you please pay him if he refuses then ask him as per the ruling of my religion and ethically also I’m bound to pay. In’Sha’Allah that will be tableegh of our religion also