Faith is the key. Here's an example from an unlikely place.

According to Genesis 1:29-31 the original diet for both humans and animals was vegetarian. Rashi confirms this:

... it will be yours for food. And to all the beasts of the earth: He equated cattle and the beasts to them [i.e. to man] regarding the food [that they were permitted to eat]. He did not permit Adam and his wife to kill a creature and to eat its flesh; only every green herb they were all permitted to eat equally. - [from Sanh. 59b]

Both humans and animals were created to be vegetarians according to Torah and our sages. This state lasted 1000 years until Noach and his family left the ark after the great flood. As Rashi explains:

When the sons of Noah came, He permitted them to eat flesh, as it is said [at Genesis 9:3]: "Every creeping thing that is alive, etc." Like the green herbs, which I permitted to the first man, I have given you everything. - [from Sanh. 59b]

So, if humans and animals lived in peace and shared a common diet, what are we to make of the statement that Abel's meat offering was more pleasing to HaShem than Cain's vegetable based offering?

The brothers lived before Noach. The text says Cain was a farmer, he grew food. His brother Abel tended the sheep.

It has been assumed by many that Abel raised and slaughtered the sheep for food, however that would contradict the command to be vegetarian. The text merely says that he tended sheep. It does not say why. Sheep have many important uses, including the making of warm clothing from their wool and producing manure for the fields. Hilchos Beis HaBechinrah 2:2 cites the ancient tradition that Adam, Cain, and Abel all brought animal offerings to the site of the future Holy Temple. This would be another reason for a religious vegetarian to raise sheep, as offerings to HaShem that they would not permitted to partake of.

There was a critical difference between the offerings of Cain and of Abel that we can learn from. Let's read the passage as we find it in the Judaica Press version:

Genesis 4:2 ...Abel was a shepherd of flocks, and Cain was a tiller of the soil.
3. Now it came to pass at the end of days, that Cain brought of the fruit of the soil an offering to the Lord.
4. And Abel he too brought of the firstborn of his flocks and of their fattest [cheleb in Hebrew], and the Lord turned to [i.e. accepted] Abel and to his offering.

See this? While Abel offered the best he had (his cheleb or "most choice") Cain, it appears, did not and therefore his sacrifice was not pleasing to G-d. Due to his high level of emuna or active faith Abel offered his very best while Cain made an offering that was devoid of kavanah (intention) and emuna.

Emuna or active faith is vital! Emuna is an inward conviction, a perception of truth that transcends rather than evades reason. With emuna we will always offer our very best, we will offer our cheleb. As a result of emuna we have certainty that our offerings will be accepted by the Holy One.

As Rebbe Nachman of Breslov teaches us:

There are various kinds of faith. There is faith that is only in the heart. But a person must have so much emuna that it spreads to all his limbs. Thus the Kabalistic writings mention that when washing one's hands to eat bread, one should raise them towards the head in order to receive holiness. Your emuna must extend into your hands in order to believe that by raising them towards your head you receive holiness. Without emuna, it is a meaningless gesture, for "All your commandments are faith [emuna]" (Psalms 119:86).

Cain did not offer his best because he lacked emuna, and so HaShem did not accept his offering. When we have faith like Abels and act out of love we can be certain that HaShem will accept our offerings no matter how humble. This knowledge frees us and empowers us to reach for the heights HaShem has prepared for us.

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