3:1 Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not.
3:4 Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law.
kosmos = mankind. (See Scofield "Matthew 4:8") .
3:7 Little children, let no man deceive you: he that doeth righteousness is righteous, even as he is righteous.
committeth sin practiseth sin practiseth also lawlessness; and sin is lawlessness.
sin Sin. (See Scofield "Romans 3:23")
3:10 In this the children of God are manifest, and the children of the devil: whosoever doeth not righteousness is not of God, neither he that loveth not his brother.
"Righteousness" here, and in the passages having marginal references to this, means the righteous life which is the result of salvation through Christ. The righteous man under law became righteous by doing righteously; under grace he does righteously because he has been made righteous Romans 3:22 .
(See Scofield "Romans 10:3")
3:13 Marvel not, my brethren, if the world hate you.
(See Scofield "1 John 3:7") .