John Gill Commentary 1 Kings 2:42

"And the king sent and called for Shimei, and said unto him, Did I not adjure thee by Jehovah, and protest unto thee, saying, Know for certain, that on the day thou goest out, and walkest abroad any whither, thou shalt surely die? and thou saidst unto me, The saying that I have heard is good." — 1 Kings 2:42 (ASV)

And the king sent and called for Shimei
He sent messengers to him, and by them ordered him to come to him, who accordingly came:

and he said to him, did not I make you swear by the Lord ;
which, though not before mentioned, was no doubt done, nor did Shimei deny it:

and protested to you ;
that is, declared before witnesses:

saying, know for certain, that on the day you go out ;
namely, out of the city of Jerusalem:

and walkest abroad any where ;
further at most than the brook Kidron, or any other place equally distant from Jerusalem, on any side of it; for when he went to Gath, he did not go over Kidron, but went the road the other way around. Kidron lay to the east, and Gath to the west of Jerusalem: now the protestation made to him was, that if he went out of Jerusalem any way,

that you shall surely die ;
it would be sure and certain death to him:

and you said to me, the word [that] I have heard [is] good ;
not only he promised to obey it, and that with an oath, but declared it was agreeable and acceptable to him, and therefore the offence was a very aggravated one.