So he offered upon the altar which he had made in Bethel the fifteenth day of the eighth month, even in the month which he had devised of his own heart; and ordained a feast unto the children of Israel: and he offered upon the altar, and burnt incense.

And he went up unto the altar which he had made in Beth-el on the fifteenth day in the eighth month, even in the month which he had devised of his own heart: and he ordained a feast for the children of Israel, and went up unto the altar, to burn incense.

And he went up to the altar, which he had built in Bethel, on the fifteenth day of the eighth month, which he had devised of his own heart: and he ordained a feast to the children of Israel, and went upon the altar to burn incense.

And he offered upon the altar that he had made in Bethel, on the fifteenth day of the eighth month, in the month which he had devised of his own heart; and he made a feast for the children of Israel, and he offered upon the altar, burning incense.

So he offered upon the altar which he had made in Beth-el the fifteenth day of the eighth month, even in the month which he had devised of his own heart; and ordained a feast to the children of Israel: and he offered upon the altar, and burnt incense.

And he offereth up on the altar that he made in Beth-El, on the fifteenth day of the eighth month, in the month that he devised of his own heart, and he maketh a festival to the sons of Israel, and offereth on the altar, to make perfume.

He went up to the altar he had made in Beth-el on the fifteenth day of the eighth month, the month fixed by him at his pleasure; and he gave orders for a feast for the people of Israel, and went up to the altar, and there he made the smoke of his offerings go up.

And he went up unto the altar which he had made in Beth-el on the fifteenth day in the eighth month, even in the month which he had devised of his own heart; and he ordained a feast for the children of Israel, and went up unto the altar, to offer.

And he ascended to the altar, which he had raised up in Bethel, on the fifteenth day of the eighth month, the day that he had decided in his own heart. And he made a solemnity to the sons of Israel, and he ascended to the altar, so that he might burn incense.

This verse belongs to 1 Kings 13 rather than to 1 Kings 12, being intended as an introduction to what follows.
Which he had devised of his own heart - The entire system of Jeroboam receives its condemnation in these words. His main fault was that he left a ritual and a worship where all was divinely authorized, for ceremonies and services which were wholly of his own devising. Not being a prophet, he had no authority to introduce religious innovations. Not having received any commission to establish new forms, he had no right to expect that any religious benefit would accrue from them. (See 1-Kings 12:26 note.)

He offered upon the altar - Jeroboam probably performed the functions of high priest himself, that he might in his own person condense the civil and ecclesiastical power.

So he offered upon the altar which he had made in Bethel the fifteenth day of the eighth month,.... As he had done in Daniel:
even in the month which he had devised of his own heart; the feast of tabernacles was of God's appointing, but the time of keeping he had devised himself, changing it from the seventh month, or Tisri, which answers to our September and October, to the eighth month, or Marchesvan, which answers to part of October and part of November:
and ordained a feast unto the children of Israel; to be observed by them as the feast of tabernacles was by the priests of Judah and Benjamin:
and he offered upon the altar, and burnt incense; which none but the priests should do; perhaps the reason why the same resentment was not shown as to Uzziah was, because this was not at the altar of the Lord: whether he burnt incense after the manner of the Jewish priests, or as the priests of Egypt did to the sun, where he had been for some time, is not certain; the former burnt incense only twice a day, morning and evening, the latter three times; at sunrising they burnt rosin, about noon myrrh, and about sun setting "kuphi", which was a compound of sixteen sorts (w).
(w) Plutarch de lside & Osiride.

Devised - Which he appointed without any warrant from God.