John Gill Commentary 2 Chronicles 12

And it came to pass, when Rehoboam had established the kingdom ,
&c.] Or when the kingdom of Rehoboam was established; the tribes of Judah and Benjamin being firmly attached to him, and great numbers from the other tribes coming over to him, and things going on peaceably and prosperously during the three years that he and his people abode by the pure worship of God:

and had strengthened himself ;
built fortified cities for the defence of himself and kingdom, (2 Chronicles 11:5–12) , he forsook the law of the Lord; after he had reigned three years, and was become strong, and thought himself safe and secure on the throne, trusting to his strength:

and all Israel with him ;
the greater part of them following the example of their king; of this defection, and the sins they fell into, see (1 Kings 14:22–24) .

And it came to pass in the fifth year of Rehoboam
In the fourth year, the apostasy of him and his people began; and, in the year following, what is next related happened, as a punishment of it:

Shishak king of Egypt came up against Jerusalem
of whom see (1 Kings 11:40) (14:25) ,

because they transgressed against the Lord
transgressed the law of the Lord by falling into idolatry and other abominable evils; the Targum is, ``against the Word of the Lord.''

With twelve hundred chariots, and threescore thousand horsemen;
and the people were without number
The foot soldiers; their number, according to Josephus ^F8 was 400,000:

that came with him out of Egypt ;
the above numerous army came from thence with him, which was famous for horses and chariots of war, see (Exodus 14:7Exodus 14:28) , what follow seem to have joined him after he came out of Egypt, or whom hesubdued in his way; the Lubim or Lybians, inhabitants of Libya, a country near Egypt the same with theLehabim; of whom see (Genesis 10:13) ,

the Sukkiims ;
who were either the Scenite Arabs, who dwelt in tents, as this word signifies; or the Troglodytes, accordingto the Septuagint and Vulgate Latin versions, who dwelt in dens and caves, in which sense the word "Succah"is sometimes used, (Job 38:40) (Psalms 10:9) and in their country was a town called Suchae, mentioned byPliny ^F9 ; they inhabited near the Red sea; and if Shishak is the same with Sesostris, as isthought, these people were subdued by him, as Herodotus ^F11 and Strabo ^F12 testify:

and the Ethiopians ;
some think these were the Cushite Arabs, and that Sesostris came into Arabia is testified by the abovewriters; though rather the proper Ethiopians are meant, since they are joined with the Lubim or Africans; andsince, as Herodotus ^F13 says, he ruled over Ethiopia; and Diodorus Siculus ^F14 says hefought with them, and obliged them to pay him tribute.

FOOTNOTES:

• F8: Antiqu. l. 8. c. 10. sect. 2.
• F9: Nat. Hist. l. 6. c. 29.
• F11: Euterpe, sive, l. 2. c. 102.
• F12: Geograph. l. 16. p. 529.
• F13: Ut supra, (Euterpe, sive, l. 2.) c. 110.
• F14: Bibliothec. l. 1. p. 50.

And he took the fenced cities which pertained to Judah
Which Rehoboam had lately built, and placed his sons in them, (2 Chronicles 11:5–12 2 Chronicles 11:23) , these he took without any opposition:

and came to Jerusalem ;
there being no army to oppose him; and so Sesostris took many countries without fighting, and among the rest Phoenicia, as Manetho ^F15 relates, in which Judea may be included.

FOOTNOTES:

• F15: Apud Joseph. contr. Apion. l. 1. c. 15.

Then came Shemaiah the prophet to Rehoboam
The same as in (2 Chronicles 11:2), there called the man of God:

and to the princes of Judah that were gathered together to Jerusalem
because of Shishak;
through fear of him, and for safety and protection from him, and to consult what was to be done at this critical juncture, whether to fight him, or make peace with him on the best terms they could:

and said unto them, thus says the Lord, you have forsaken me;
his law, his word, worship, and ordinances, (2 Chronicles 12:1),

and therefore have I also left you in the hand of Shishak;
suffered him to invade their land, take their fenced cities, and come up to Jerusalem without any opposition, as a punishment of their apostasy; and to explain this providence to them, and call them to repentance, was the prophet sent.