Albert Barnes Commentary 1 Kings 8:54

"And it was so, that, when Solomon had made an end of praying all this prayer and supplication unto Jehovah, he arose from before the altar of Jehovah, from kneeling on his knees with his hands spread forth toward heaven." — 1 Kings 8:54 (ASV)

If Solomon's prayer is, as it certainly appears to be, a genuine document from that time, preserved in the archives to which the authors of both Kings and Chronicles had access, then all theories about a late origin for Deuteronomy must be regarded as baseless.

While references to other portions of the Pentateuch are not infrequent, the prayer's language is mainly modeled on Deuteronomy, whose promises and threats are continually on the writer's mind.