Jacob addresses his people at a crucial juncture in their development. They are a new nation, and they have been taught a new religion and new precepts. There were those among them who had been obedient to God’s laws, as evidenced when Jacob told them in verse 4 above that they had, “as of yet … been obedient unto the word of the Lord.”
Nevertheless, Jacob has not come to speak of obedience, but rather of the path to disobedience. That same people of whom he said had as yet been obedient, here must be spoken to “concerning the wickedness of your hearts.”
Verse 8 is particularly poignant. Jacob knows that they have come expecting some sermon that might make them feel good, to feel “the word which healeth the wounded soul.” That is not what they are going to get. It will be a sermon to open wounds with the hope of cauterizing them, not to cover them and allow them to fester.