It is God Who Gives the Increase

We are here taught to have a continual regard to the divine Providence in all the concerns of this life. Solomon was cried up for a wise man, and would be apt to lean to his own understanding and forecast, and therefore his father teaches him to look higher, and to take God along with him in his undertakings. He was to be a man of business, and therefore David instructed him how to manage his business under the direction of his religion…We must have an eye to God…in all the affairs and business of the family, even of the royal family, for kings' houses are no longer safe than while God protects them. We must depend upon God's blessing and not our own contrivance…[but] by his providence and blessing, those labour in vain, though ever so ingenious, that build it. We may understand it of the material house: except the Lord bless the building it is to no purpose for men to build, any more than for the builders of Babel, who attempted in defiance of heaven…If the model and design be laid in pride and vanity, or if the foundations be laid in oppression and injustice, God certainly does not build there; nay, if God be not acknowledged, we have no reason to expect his blessing, and without his blessing all is nothing. – Matthew Henry