John Gill Commentary 1 Chronicles 22

Then David said
Within himself, or to some principal persons about him:

this is the house of the Lord God ;
the place where the temple was to be built, hinted at in (Deuteronomy 12:5) and elsewhere; the meaning is, here, or in "this" place, shall be the house of God, so Noldius ^F15 , for as yet there were none; but it was now made known to David that here it should be built, and so the words in (2 Chronicles 3:1) should be rendered,

then Solomon began to build the house of the Lord in Jerusalem, which
was shown to David his father, which he prepared in the place of David,
that which he bought in the threshing floor of Ornan the Jebusite: and
this is the altar for the burnt offering for Israel ;
not which he had built here; but this is the place where one should be built for the people of Israel to bring their offerings to, and to be here offered for them by the priests: this he said by a divine impulse upon his mind, or which he concluded from the acceptance of his sacrifice here, signified by fire that came down from heaven and consumed it; and this being in the threshingfloor of the Jebusites, might prefigure the church of God to be built up among the Gentiles.

FOOTNOTES:

• F15: Ebr. Concord. Part. p. 352. No. 1257.

And David commanded to gather together the strangers that were
in the land of Israel
The proselytes, as the Septuagint and Vulgate Latin versions; that is, proselytes of the gate, who submitted to the seven precepts of Noah, were admitted to dwell in the Cities of Israel, see (Genesis 9:4) and these were ordered to be got together to be employed in building the temple, and making preparations for it; and that partly because they were better artificers than the Israelites, who were chiefly employed in husbandry and cattle, and partly that the Israelites, who were freemen, might not be put to hard service; but chiefly this was for the sake of a mystery in it, denoting that the Gentiles would be concerned in building the spiritual house and church of God, the temple was a type and figure of, see (Zechariah 6:15)

and he set masons to hew wrought stones to build the house of God ;
to dig them out of the quarries, and fit them for the building.

And David prepared iron in abundance for the nails for the
doors of the gates, and for the joinings
Great plenty of iron to make nails of for joining the boards together, of which the doors and gates were to be made, and for the fastening of the hinges of them:

and brass in abundance without weight ;
for making the altar of brass, and the laver of brass, and other vessels. Brass was much used by the Heathens in sacred things, as Macrobius ^F16 observes.

FOOTNOTES:

• F16: Saturnal. l. 5. c. 19.

Also cedar trees in abundance
To be sawed into boards and planks for the ceiling, wainscotting, and flooring of the temple, and other things:

for the Zidonians, and they of Tyre, brought much cedar wood to David ;
from Mount Lebanon, which was chiefly in their possession; and which they did either of themselves as a free gift and present to him, or at his request, for which he paid them; and this is another thing prefiguring the help of the Gentiles in building up the church of Christ in Gospel times.

And David said, Solomon my son is young and tender
Jarchi supposes he was about twelve years of age, though he observes that the same word is used of Joshua when forty two years of age; it is probable Solomon might be now about twenty:

and the house that is to be builded for the Lord must be exceeding
magnificent, of fame and of glory throughout all countries :
and such was the temple built by Solomon; it was renowned throughout the whole earth; never was there a temple equal to it, no, not the famous temple of Diana at Ephesus, built by the assistance of many kings, and at the expense of all Asia, and was two hundred years in building:

I will therefore now, make preparation for it ;
seeing his son was so young, and this building to be so magnificent, though he himself was not admitted to build it:

so David prepared abundantly before his death ;
of which we have an after account in this chapter, and more largely in (1 Chronicles 28:1-29:30) .