New Revised Standard Version
Therefore, O LORD, God of Israel, keep for your servant, my father David, that which you promised him, saying, ‘There shall never fail you a successor before me to sit on the throne of Israel, if only your children keep to their way, to walk in my law as you have walked before me.’

Contemporary English Version
You promised that someone from his family would always be king of Israel, if they do their best to obey you, just as he did.

New American Bible
And now, LORD, God of Israel, keep toward your servant, David my father, what you promised: There shall never be wanting someone from your line to sit before me on the throne of Israel, provided that your descendants keep to their way, walking by my law, as you have.

Douay-Rheims Bible
Now then, O Lord God of Israel, fulfil to thy servant David my father, whatsoever thou hast promised him, saying: There shall not fail thee a man in my sight, to sit upon the throne of Israel: yet so that thy children take heed to their ways, and walk in my law, as thou hast walked before me.

Now then, O Lord God of Israel, fulfil to thy servant David my father, whatsoever thou hast promised him, saying: There shall not fail thee a man in my sight, to sit upon the throne of Israel: yet so that thy children take heed to their ways, and walk in my law, as thou hast walked before me.

keep

Ezekiel 36:37 Thus saith the Lord God: Moreover in this shall the house of Israel find me, that I will do it for them: I will multiply them as a flock of men,

John 15:14,15 You are my friends, if you do the things that I command you. . . .

saying

2 Chronicles 7:18 I will raise up the throne of thy kingdom, as I promised to David thy father, saying: There shall not fail thee a man of thy stock to be ruler in Israel.

2 Samuel 7:12-16 And when thy days shall be fulfilled, and thou shalt sleep with thy fathers, I will raise up thy seed after thee, which shall proceed out of the bowels, and I will establish his kingdom. . . .

1 Kings 2:4 That the Lord may confirm his words, which he hath spoken of me, saying: If thy children shall take heed to their ways, and shall walk before me in truth, with all their heart, and with all their soul, there shall not be taken away from thee a man on the throne of Israel.

1 Kings 6:12 As for this house, which thou art building, if thou wilt walk in my statutes, and execute my judgments, and keep all my commandments, walking in them, I will fulfil my word to thee, which I spoke to David thy father.

Psalm 132:12 If thy children will keep my covenant, and these my testimonies which I shall teach them: Their children also for evermore shall sit upon thy throne.

There shall not fail thee a man [heb]

to walk

Psalm 26:3 For thy mercy is before my eyes; and I am well pleased with thy truth.

Psalm 119:1 Blessed are the undefiled in the way, who walk in the law of the Lord.