‘If a brother or sister be naked and in lack of daily food, and one of you say to them, “Go in peace, be you warmed and filled”, but you do not give them the things needful to the body, what does it profit (‘what is the benefit of that')?'
Once again his thoughts turn for an illustration to the poor. He pictures a fellow Christian without proper clothing and short of nourishment, and the supposed Christian saying piously, ‘Go in peace.May God warm you and fill you' (the passive tense regularly indicates God's action). But of what use is that if God's professed servant fails to warm and fill them? Who else can God use for the purpose? It is piously asking God to do what in fact He expects THEM to do. It is clearly making a mockery of God and demonstrating that they do not go along with Him either in His thoughts or in His purposes. Their faith is thus shown not to be genuine.
This accusation would fit Gentiles more than Jews, for if there was one thing that Jews were good at it was at giving alms and making provision for the poor, supporting the case that the letter is to the whole church.