Genesis 4:6

Why art thou wroth? Here it is evident, as in vs. 14 and 16, that God did not cease making personal contact with men at the time He expelled them from the garden. The rejection of Cain’s offering did not necessarily mean the rejection of Cain himself. In mercy and patience God was ready to give him another chance. Though clearly manifesting His displeasure by rejecting the offering, God appeared to the sinner and reasoned with him in an attempt to persuade him of the error of his way and the unreasonableness of his anger. God spoke to Cain as to a willful child, to draw out into the open that which was lurking like a wild beast before the door of his heart. The question Why was designed to lead Cain to acknowledge the baselessness of his anger. For the rejection of his offering there must be a valid reason, which he should discover and eliminate.