He's saying the man is a political animal who realize himself in a political community and could not be without his fellow citizens. Ethic and politic are eminantly linked : the final purpose being happiness and virtue by citizens dominated by the law. The ethic determined the ends and nature of virtue which leads to happiness...
In order to do so you need to look for friendship and intellectual reflection....Friendship=1 soul in 2 bodies
And the sacrifice of himself is needed to achieve virtue