1 John 3:1

Behold what manner of love
See, take notice, consider, look by faith, with wonder and astonishment, and observe how great a favour, what an instance of matchless love, what a wonderful blessing of grace,

the Father hath bestowed upon us:
the Father of Christ, and the Father of us in Christ, who hath adopted us into his family, and regenerated us by his grace, and hath freely given us the new name:

that we should be called the sons of God.
The Alexandrian copy, and some others, and the Vulgate Latin version, add, "and we are", or "be"; and the Ethiopic version, "and have been"; for it is not a mere name that is bestowed, but the thing itself in reality; and in the Hebrew language, "to be called", and "to be", are terms synonymous; see ( Isaiah 9:6 ) ( Hosea 1:10 ) ; in what sense the saints are the sons of God; (See Gill on Galatians 4:6); this blessing comes not by nature, nor by merit, but by grace, the grace of adoption; which is of persons unto an inheritance they have no legal right unto; the spring of it is the everlasting and unchangeable love of God, for there was no need on the adopter's side, he having an only begotten and beloved Son, and no worth and loveliness in the adopted, they being by nature children of wrath; it is a privilege that exceeds all others, and is attended with many; so that it is no wonder the apostle breaks out in this pathetic manner, and calls upon the saints to view it with admiration and thankfulness:

therefore the world knoweth us not;
that is, the greater part of the world, the world that lies in wickedness, the men of the world, who have their portion in this life, whom the god of this world has blinded, and who only mind the things of the world, and are as when they came into it, and have their conversation according to the course of it; these do not know the saints are the sons of God; the new name of sons is what no man knoweth but he that receiveth it; they do not own the saints as theirs, as belonging to them, but reckon them as the faith of the world, and the offscouring of all things; nor do they love them, and that because they are not their own, but hate them and persecute them: the reason is,

because it knew him not;
neither the Father, whose sons they are, and who has bestowed the grace upon them; wherefore they know not, and disown and persecute his children; see ( John 17:25 ) ( 15:21 ) ( 16:3 ) ; nor the Lord Jesus Christ, the only begotten of the Father, the firstborn among many brethren; who, though he made the world, and was in it, was not known by it, but was hated, abused, and persecuted; and therefore it need not seem strange that the saints, who are the sons of God by adoption, should be treated in like manner.