Because it is written
In ( Leviticus 11:44 ) ( 19:2 ) ( 20:7 )
be ye holy, for I am holy:
an argument the apostle knew must have weight with these persons, who were chiefly Jews, scattered abroad among the Gentiles, and had a value for the Scriptures of truth; and therefore, as the argument for holiness of life, from the nature and perfections of God, is strong, it must receive additional strength from this being the declared will of God, even their sanctification on this account; and though holiness, equal to God, is never to be attained to by a creature, yet so far as it is capable of it, it is desirable, because agreeable both to the nature and will of God, by all such who are truly his children, who love his name, adore his perfections, give thanks at the remembrance of his holiness, fear his goodness, and obey his will.