And ye know that he was manifested to take away our sins; and in him is no sin.
Additional proof of the incompatibility of sin and sonship: the very object of Christ's manifestation in the flesh was to take away (by one act) entirely [aorist, aree (G142)] all sins, as the scapegoat did typically. And - another proof.
In him is no sin - not 'was,' but "is," as 1 John 3:7, "He is righteous," and 1 John 3:3. Therefore we are to be so.