New Revised Standard Version
I will establish his kingdom forever if he continues resolute in keeping my commandments and my ordinances, as he is today.’

Contemporary English Version
If he continues to obey my laws and commands, his kingdom will never end."

New American Bible
I will establish his kingdom forever, if he perseveres in carrying out my commandments and ordinances as he does now.

Douay-Rheims Bible
And I will establish his kingdom for ever, it he continue to keep my commandments, and my judgments, as at this day.

And I will establish his kingdom for ever, it he continue to keep my commandments, and my judgments, as at this day.

Moreover

Psalm 89:28-37 I will keep my mercy for him for ever: and my covenant faithful to him. . . .

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.

Daniel 2:44 But in the days of those kingdoms, the God of heaven will set up a kingdom that shall never be destroyed, and his kingdom shall not be delivered up to another people: and it shall break in pieces, and shall consume all these kingdoms: and itself shall stand for ever.

if

1 Chronicles 22:13 For then thou shalt be able to prosper, if thou keep the commandments, and judgments, which the Lord commanded Moses to teach Israel: take courage and act manfully, fear not, nor be dismayed.

1 Kings 6:12,13 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. . . .

1 Kings 9:4,5 And if thou wilt walk before me, as thy father walked, in simplicity of heart, and in uprightness: and wilt do all that I have commanded thee, and wilt keep my ordinances, and my judgments, . . .

1 Kings 11:9-13 And the Lord was angry with Solomon, because his mind was turned away from the Lord, the God of Israel, who had appeared to him twice; . . .

constant [heb] strong

1 Chronicles 28:10 Now therefore seeing the Lord hath chosen thee to build the house of the sanctuary, take courage, and do it.

Joshua 1:6,7 Take courage, and be strong: for thou shalt divide by lot to this people the land for which I swore to their fathers, that I would deliver it to them. . . .

1 Kings 2:2-4 I am going the way of all flesh: take thou courage and shew thyself a man. . . .

as at this day

1 Kings 8:61 Let our hearts also be perfect with the Lord our God, that we may walk in his statutes, and keep his commandments, as at this day.

1 Kings 11:4 And when he was now old, his heart was turned away by women to follow strange gods: and his heart was not perfect with the Lord his God, as was the heart of David, his father.