2 Samuel 18:12
And the man said unto Joab, Though I should receive a thousand shekels of silver in mine hand, yet would I not put forth mine hand against the king’s son: for in our hearing the king charged thee and Abishai and Ittai, saying, Beware that none touch the young man Absalom.
This saying belongs to the history of Absalom's rebellion against David, which ended when David's forces defeated the rebels and Absalom was slain. Absalom was David's beloved son, yet he rose up and pursued his father in war, and when he was defeated and killed it brought David great distress. Before the battle David had openly charged Joab and Abishai and Ittai to deal gently and do no harm to Absalom, and that order to spare him was heard and known among his men.
The speaker was a common soldier who came upon Absalom caught and helpless but refused to lift his hand against the king's son. He held back because he feared to disobey the king's express command, even for the offer of a thousand shekels of silver in his hand. Instead of striking himself, he went and reported to Joab what he had seen.