Albert Barnes Commentary 1 Kings 9:25

"And three times a year did Solomon offer burnt-offerings and peace-offerings upon the altar which he built unto Jehovah, burning incense therewith, [upon the altar] that was before Jehovah. So he finished the house." — 1 Kings 9:25 (ASV)

Three times—That is, the three solemn feasts: the Feast of Unleavened Bread, the Feast of Weeks, and the Feast of Tabernacles.

Did Solomon offer... and he burnt incense—Not with his own hand, but by his priests (1 Kings 8:6; 2 Chronicles 5:7–14). In sacred, as in ordinary, history, people are said to do that which they cause to be done.