4. more excellent sacrifice--because offered in faith. Now faith must have some revelation of God on which it fastens. The revelation in this case was doubtless God's command to sacrifice animals ("the firstlings of the flock") in token of the forfeiture of men's life by sin, and as a type of the promised bruiser of the serpent's head (Ge 3:15), the one coming sacrifice: this command is implied in God's having made coats of skin for Adam and Eve (Ge 3:21): for these skins must have been taken from animals slain in sacrifice: inasmuch as it was not for food they were slain, animal food not being permitted till after the flood; nor for mere clothing, as, were it so, clothes might have been made of the fleeces without the needless cruelty of killing the animal; but a coat of skin put on Adam from a sacrificed animal typified the covering or atonement (the Hebrew for atone means to cover) resulting from Christ's sacrifice. The Greek is more literally rendered [KENNICOTT] by WYCLIFFE, "a much more sacrifice"; and by Queen Elizabeth's version "a greater sacrifice." A fuller, more ample sacrifice, that which partook more largely and essentially of the true nature and virtue of sacrifice [ARCHBISHOP MAGEE]. It was not any intrinsic merit in "the firstling of the flock" above "the fruit of the ground." It was God's appointment that gave it all its excellency as a sacrifice; if it had not been so, it would have been a presumptuous act of will-worship (Col 2:23), and taking of a life which man had no right over before the flood (Ge 9:1-6). The sacrifice seems to have been a holocaust, and the sign of the divine acceptance of it was probably the consumption of it by fire from heaven (Ge 15:17). Hence, "to accept" a burnt sacrifice is in Hebrew "to turn it to ashes" (Ps 20:3, Margin). A flame seems to have issued from the Shekinah, or flaming cherubim, east of Eden ("the presence of the Lord," Ge 4:16), where the first sacrifices were offered. Cain, in unbelieving self-righteousness, presented merely a thank offering, not like Abel feeling his need of the propitiatory sacrifice appointed on account of sin. God "had respect (first) unto Abel, and (then) to his offering" (Ge 4:4). Faith causes the believer's person to be accepted, and then his offering. Even an animal sacrifice, though of God's appointment, would not have been accepted, had it not been offered in faith.
      he obtained witness--God by fire attesting His acceptance of him as "righteous by faith."
      his gifts--the common term for sacrifices, implying that they must be freely given.
      by it--by faith exhibited in his animal sacrifice.
      dead, yet speaketh--His blood crying front the ground to God, shows how precious, because of his "faith," he was still in God's sight, even when dead. So he becomes a witness to us of the blessed effects of faith.

JFB.