Jamieson, Fausset and Brown on 2 Samuel 14:28

28. So Absalom dwelt two full years in Jerusalem, and saw not the king's face--Whatever error David committed in authorizing the recall of Absalom, he displayed great prudence and command over his feelings afterwards--for his son was not admitted into his father's presence but was confined to his own house and the society of his own family. This slight severity was designed to bring him to sincere repentance, on perceiving that his father had not fully pardoned him, as well as to convince the people of David's abhorrence of his crime. Not being allowed to appear at court, or to adopt any state, the courtiers kept aloof; even his cousin did not deem it prudent to go into his society. For two full years his liberty was more restricted, and his life more apart from his countrymen while living in Jerusalem, than in Geshur; and he might have continued in this disgrace longer, had he not, by a violent expedient, determined (2Sa 14:30) to force his case on the attention of Joab, through whose kind and powerful influence a full reconciliation was effected between him and his father.