Here's a great illustration of the gospel from an old book. The book is The Second Mile by Fosdick. I have no idea how old it is since a friend loaned me the book and lo and behold it is missing the first ten pages. What to do? Read it anyway.
This is great:
"It was in escaping from this legalism [the legalism of rule-keeping and counting up your good deeds and bad] that Paul said he became a Christian. No man is really a Christian until he has escaped it. If a boy, adopted into a strange home, and unruly in his new surroundings, should perforce be given a set of regulations which he must observe, he might become more orderly, but he would hardly by that alone become a true son. But if some day the love of the father or mother should be persuasively revealed to him, so that the love that had been there always laid masterful hold on him, and his love, newly born, should spring up in answer, flooding his spirit with its loyalty, and if, knowing the new life in him, he should take the rules and tear them up, saying "Because I love you I will do all these and much more beside," then a true son would have been begotten. He would have been "born again."
"If ye love me, ye WILL keep my commandments," said Jesus and this statement of inevitable consequence is summed up in Paul's sublime word, "Love is the fulfilling of the law." Apart from love a man cannot keep so many rules or do so many deeds as to make himself a Christian.