Why did God respect Abel's sacrifice?

Help will be valued upon Genesis 4:4, 5, where we read that God had “respect” to Abel and his offering and not to Cain and his, and Romans 2:11, where it is said that there is “no respect of persons with God.”

We can be quite sure that this latter verse is ever and absolutely true. The Greek word, “to have respect of persons,” means, “to receive the face of a person,” i.e. to look at the outward appearance—at the gold ring and the gay clothing, at the feature and the stature, etc., whereas we know that “God looks, not at the outward appearance, but at the heart.” When, therefore, we read that God had respect to Abel and his offering, we must divest ourselves of any idea of favouritism or unfair preference on His part. In fact, the Hebrew word in Genesis 4, “to have respect,” has no thought of respect of persons, but of looking to someone, or something. The word is used in Psalm 119:117—”I will have respect unto thy statutes continually”; again in 2 Samuel 22:42—”They looked but there was none to save,” and also in Isaiah 17:7—”In that day shall a man look to his Maker.” We may be sure that had it been righteously possible, God would have accepted Cain as well as Abel. The key to the verse is in Hebrews 11:4—”By faith Abel offered unto God a more excellent sacrifice than Cain . . . God testifying of his gifts.” It was not that Abel was “more excellent” than Cain, though very likely he was, but that his sacrifice was more excellent; so that God simply had respect to Abel because of his sacrifice. The expression, “by faith,” shows, I think, conclusively that God had revealed how his creatures were to approach him, “for faith cometh by hearing, and hearing by the word of God.” No doubt, Cain’s sacrifice was beautiful enough, but it was Cain’s way, not God’s. It was merely the work of his hands-of the same vegetable kingdom as the fig-leaves of which Adam and Eve had made themselves aprons. Abel offered from the first-fruits of  the flock and of the fat thereof, i.e. the slain lamb. In Abel’s offering there were two things : there was something which spoke of his repentance, it was as though he admitted that he deserved the death of the victim; and there was something, too, which spoke of the lamb of God, without blemish, slain before the foundation of the world. How far Abel apprehended the truth we cannot say; he obeyed and allwas known to God. We are blessed according to His appreciation of the infinite Person and work of Christ, not according to ours, which, however, does determine our enjoyment of our blessings.