Why did God reject Cain's sacrifice?

“By faith Abel offered unto God a more excellent sacrifice than Cain. . . God testifying of his gifts, and by it he being dead yet speaketh.”Hebrews11:4

Why were Abel and his offering accepted, and Cain and his offering rejected? Does the expression “more excellent” imply that there was something excellent in that of Cain?

The word translated, “more excellent,” is literally “more, “or’ ‘greater,” and is used either of quantity or quality, here clearly of the latter. It does not imply any excellence in Cain’s offering, otherwise we should not read, “but unto Cain and to his offering God had not respect.” Also later God said to him, “If thou doest well (i.e., come like Abel with the slain victim, implying that Cain had not done well in offering his fruit of the earth), but if thou doest not well (i.e., persist in thy refusal of that offering;) sin’ lieth at the door; i.e., croucheth like a wild beast ready to spring. There can be no reasonable doubt that God had revealed to His fallen creatures how they must approach to Him—even by the minhab or approach offering—a lamb of the flock. Clearly this was to be slain, as the expression—”of the fat thereof” shows. Had there been no such revelation, how could Abel have had “faith” to draw near in this way?

I remember years ago seeing a blind Kabyle reading in Braille type by the wayside in North Africa, what I learned to be this fourth chapter of Genesis. When we asked him why God accepted Abel’s offering, he replied, “There was something in it which spoke of the Messiah.” This is true; no doubt that sacrifice was a type of the Lamb of God slain at Calvary, and foreshadowed the bruising of the Kinsman’s heel. Abel confessed himself worthy of death and appropriated the death of the victim in his stead. Cain’s offering was of the same vegetable kingdom as the fig-leaves of the aprons of Adam and Eve, and as the host of flour and water, which the Romanist and Ritualist offer on their “altars,” all of which are bloodless offerings and powerless to remit