Three years - i. e., during the first three years of Rehoboam's reign. In the fourth year an apostasy took place, which neutralized all the advantages of the immigration (marginal reference). In the fifth the apostasy was punished by the invasion and success of Shishak 2 Chronicles 12:2.

For three years they walked in the way of David - During this time he prospered; but for fourteen years after this he and the people were unfaithful to the Lord, except at such intervals as the hand of God's judgments was upon them.

So they strengthened the kingdom of Judah,.... Made it more numerous, and in a better condition to defend itself:

and made Rehoboam son of Solomon strong three years; established him on the throne, strengthened the government in his hands, and were the means of preserving him in the pure worship of God for the space of time mentioned, the reason of which follows:

for three years they walked in the way of David and Solomon; in their good ways, which were according to the rule of the divine word; and which, as they refer to the whole of David's life and reign, some particular actions excepted, so to the former part of Solomon's reign, before he fell into idolatry, and to the latter part of it after his repentance; for that he did repent is by some concluded from hence, and may be more strongly from the book of Ecclesiastes, written by him in his old age. This is to be understood both of Rehoboam and his people, who after three years forsook the law of the Lord, 2 Chronicles 12:1.

These immigrants - priests, Levites, and pious worshippers of Jahve-made the kingdom of Judah strong, by strengthening the religious foundation on which the kingdom was founded, and made Rehoboam strong three years, so that they (king and people) walked in the way of David and Solomon. The strengthening lasted only three years-only while the opposition to Jeroboam's action in the matter of religion was kept alive by the emigration of the pious people from the ten tribes. What occurred after these three years is narrated only in 2 Chronicles 12. - Here there follows, in

So they strengthened the kingdom of Judah, and made Rehoboam the son of Solomon strong, three years: for three years they {f} walked in the way of David and Solomon.

(f) As long as they feared God, and set forth his word, they prospered.

11:17 So they strengthened the kingdom of Judah - Not only by the addition of so many persons to it: but by their piety and prayers they procured a blessing upon the kingdom which was a sanctuary to them. They made him strong three years; for so long he served God; but when he forsook God, none could strengthen him. We retain our strength as long as we cleave to God and our duty, and no longer. And Solomon - This honourable mention of Solomon, as a pattern of piety, is a considerable evidence of his true repentance before his death.

17. they strengthened the kingdom of Judah-The innovating measures of Jeroboam were not introduced all at once. But as they were developed, the secession of the most excellent of his subjects began, and continuing to increase for three years, lowered the tone of religion in his kingdom, while it proportionally quickened its life and extended its influence in that of Judah.

11:13-23 When the priests and Levites came to Jerusalem, the devout, pious Israelites followed them. Such as set their hearts to seek the Lord God of Israel, left the inheritance of their fathers, and went to Jerusalem, that they might have free access to the altar of God, and be out of the temptation to worship the calves. That is best for us, which is best for our souls; in all our choices, religious advantages must be sought before all outward conveniences. Where God's faithful priests are, his faithful people should be. And when it has been proved that we are willing to renounce our worldly interests, so far as we are called to do so for the sake of Christ and his gospel, we have good evidence that we are truly his disciples. And it is the interest of a nation to protect religion and religious people.