Romanos 7:5

‘For when we were in the flesh, the sinful passions, which were through the law, wrought in our members to bring forth fruit unto death.'

For when we were living our old lives under the Law (we were in the flesh, following the ways of the flesh, compare Romanos 8:5) the sinful passions within us were stirred up by the Law, and the Law therefore worked within us making us produce fruit which could only result in death (compare Romanos 1:32; Gálatas 5:17; Gálatas 5:19). Here is one example of why the Law failed. It failed because rather than curbing sin, it aroused it in men's hearts. And it failed because we were ‘in the flesh'.