According to the author of 1 Kings, the king reminded Shimei that he had promised to obey and not leave, because if he did, something bad would happen. Shimei had agreed that this rule was fair and good.
1 Kings 2:42: And the king sent and called for Shimei, and said unto him, Did I not make thee to swear by the LORD, and protested unto thee, saying, Know for a certain, on the day thou goest out, and walkest abroad any whither, that thou shalt surely die? and thou saidst unto me, The word [that] I have heard [is] good.
This verse advises against swearing oaths, which contradicts the command Solomon gives to Shimei in 1 Kings 2:42 regarding his oath.
James 5:12: But above all things, my brethren, swear not, neither by heaven, neither by the earth, neither by any other oath: but let your yea be yea; and [your] nay, nay; lest ye fall into condemnation.