Fourth ...

Fourth : Allah’s arresting him on account of doing an undesirable thing and of avoiding a desirable thing so that he may know that when Allah catches hold of him because of avoiding non-obligatory deeds He would surely not be lenient to him in the matter of obligatory duties, that is, in avoiding compulsory things and indulging in prohibited matters.

In short, when these qualities join together in somebody he will be sinless and it is true that his strength is not wasted in sinful deeds otherwise he would not be worthy of praise for giving up sins. For him…