Matthew Henry Commentary 1 Kings 2:1-4

"Now the days of David drew nigh that he should die; and he charged Solomon his son, saying, I am going the way of all the earth: be thou strong therefore, and show thyself a man; and keep the charge of Jehovah thy God, to walk in his ways, to keep his statutes, [and] his commandments, and his ordinances, and his testimonies, according to that which is written in the law of Moses, that thou mayest prosper in all that thou doest, and whithersoever thou turnest thyself. That Jehovah may establish his word which he spake concerning me, saying, If thy children take heed to their way, to walk before me in truth with all their heart and with all their soul, there shall not fail thee (said he) a man on the throne of Israel." — 1 Kings 2:1-4 (ASV)

David's charge to Solomon is to keep the charge of the Lord. The authority of a dying father is significant, but it is nothing compared to that of a living God. God promised David that the Messiah should come from his descendants, and that promise was absolute; but the promise that he would not fail to have a descendant on the throne of Israel was conditional. If he walks before God in sincerity, with zeal and resolution, and to do so, he must take heed to his way. (1 Kings 2:5–11)