Verse 3
Purifieth himself; that is, his hope of being hereafter joined to Christ in happiness and glory, leads him to seek now to resemble him in character.

Verse 5
He was manifested; Christ was manifested, that is, appeared upon this earth.

Verse 6
Whosoever sinneth; that is, willingly and habitually.

Verse 15
Is a murderer; in the spirit and temper of his mind.

Verse 16
To lay down our lives, to be willing to lay them down.

Verse 18
Not--in word, neither in tongue, not in empty professions.

Verse 19
And hereby; that is, by the habitual temper and spirit of our minds.

Verse 20
Our heart; our conscience.