Chronicles I 28:9

9 And now, son Solomon, know the God of thy fathers, and serve him with a perfect heart and willing soul: for the Lord searches all hearts, and knows every thought: if thou seek him, he will be found of thee; but if thou shouldest forsake him, he will forsake thee for ever.

Chronicles I 28:9 Meaning and Commentary

1 Chronicles 28:9

And thou, Solomon my son
Who was present in this assembly, and presented to them by David as his successor, and their future king: and having addressed them, he turns himself to him, and exhorts him, saying,

know thou the God of thy father;
who was his Father and covenant God, and whom he served and worshipped, and who had bestowed upon him many favours, both temporal and spiritual; and having had such an experience of his goodness, he exhorts his son to seek to know more and more of him, and to own and acknowledge him as his God, and to love and fear him:

serve him with a perfect heart, and with a willing mind;
cordially and sincerely, cheerfully and freely, neither in an hypocritical manner, nor through force and constraint, nor with loathing and weariness:

for the Lord searcheth all hearts;
the hearts of all men, even of kings, and knows from what principles and with what views and in what manor they serve him:

and understandeth all the imaginations of the thought;
not only the thoughts of the heart, when regularly formed and ranged in order, hut even the very beginning of them, the first motions of the mind, and before they are well formed, see ( Genesis 6:5 ) ( Psalms 139:2 )

if thou seek him;
by prayer and supplication in his house and ordinances:

he will be found of thee;
grant his presence and bestow his favours, see ( Isaiah 4:6 )

but if thou forsake him:
his word, his ways, his worship:

he will cast thee off for ever;
from being king, or enjoying that peace, prosperity, and happiness, which otherwise would be enjoyed.

Chronicles I 28:9 In-Context

7 And I will establish his kingdom for ever, if he continue to keep my commandments, and my judgments, as this day.
8 And now before the whole assembly of the Lord, and in the audience of our God, keep and seek all the commandments of the Lord our God, that ye may inherit the good land, and leave it for your sons to inherit after you for ever.
9 And now, son Solomon, know the God of thy fathers, and serve him with a perfect heart and willing soul: for the Lord searches all hearts, and knows every thought: if thou seek him, he will be found of thee; but if thou shouldest forsake him, he will forsake thee for ever.
10 See now, for the Lord has chosen thee to build him a house for a sanctuary, be strong and do .
11 And David gave Solomon his son the plan of the temple, and its buildings, and its treasuries, and its upper chambers, and the inner store-rooms, and the place of the atonement,

The Brenton translation of the Septuagint is in the public domain.