Repentance is of such importance that there is no being saved without it…It is a great duty incumbent upon Christians solemnly to repent and turn unto God…That religion which is not built upon this foundation must needs fall to the ground.
Repentance is a grace required under the gospel. Some think it legal; but the first sermon that Christ preached, indeed, the first word of his sermon, was ‘Repent’ (Matt. 4.17). And his farewell that he left when he was going to ascend was that ‘repentance should be preached in his name’ (Luke 22.47)…Repentance is not arbitrary. It is not left to our choice whether or not we will repent, but it is an indispensable command. God has enacted a law in the High Court of heaven that no sinner shall be saved except the repenting sinner, and he will not break his own law.
Some bless themselves that they have a stock of knowledge, but what is knowledge good for without repentance? It is better to mortify one sin than to understand all mysteries. Impure speculatists do but resemble Satan transformed into an angel of light. Learning and a bad heart is like a fair face with a cancer in the breast. Knowledge without repentance will be but a torch to light men to hell. ~Thomas Watson, The Doctrine of Repentance Source
Repentance will cost you more than a few cheap words against sin! ~ John Flavel