New Defender's Study Bible Notes
127:3 his reward. It would be fitting for Hezekiah to select this song of David “for Solomon” as the central psalm of his fifteen “Songs of degrees.” He had been without a son himself until three years after His miraculous healing (II Kings 21:1). The birth of his son was necessary for God to fulfill His original promise to David (II Samuel 7:13). This promise was fulfilled precursively in Solomon but eventually to culminate in the Messiah. It would be natural for Hezekiah to appropriate this joyful “Song for Solomon” to reflect his own joy over the birth of his own son in the line of the promised Messiah. The children referred to here may well be either actual physical progeny or spiritual children in the Lord. Especially in the latter case, “happy is the man that hath his quiver full of them” (Psalm 127:5).
127:4 children of thy youth. This verse is, appropriately enough, the central verse in the fifteen Songs of Degrees.