How can a man be just with God?

Only by genuine faith (Faith = Pistis a total unshakable trust in, reliance upon and cleaving to....believing = pisteuo the verb form of the noun pistis and it means one who is actually and actively trusting in, relying on, and cleaving to someone or something which in this case is the Messiah (Y'shua a contraction of the Lord's salvation) and the redemptive work for which He was sent to do on your behalf). It is not enough to believe there is a God (as in "I believe in God") mentally assirting He is real....but rather to believe God (this is the faith that justifies because it knows Him and thus can really and truly trust in Him in this way) do this one must begin here (John 3:3-8; Acts 2:38)