".... we should not waste time encouraging vegetarianism as opposed to meat eating. We want to encourage prasadam taking and that is automatically vegetarian."
Srila Prabhupada Letter, 01-09-76
"Remnants of food may be eaten only when they are part of a meal that was first offered to the Supreme Lord or first eaten by saintly persons, especially the spiritual master. Otherwise the remnants of food are considered to be in the mode of darkness, and they increase infection or disease. Such foodstuffs, although very palatable to persons in the mode of darkness, are neither liked nor even touched by those in the mode of goodness. The best food is the remnants of what is offered to the Supreme Personality of Godhead. In Bhagavad-gita the Supreme Lord says that He accepts preparations of vegetables, flour and milk when offered with devotion. Patram puspam phalam toyam. Of course, devotion and love are the chief things which the Supreme Personality of Godhead accepts. But it is also mentioned that the prasadam should be prepared in a particular way. Any food prepared by the injunctions of the scripture and offered to the Supreme Personality of Godhead can be taken even if prepared long, long ago, because such food is transcendental. Therefore to make food antiseptic, eatable and palatable for all persons, one should offer food to the Supreme Personality of Godhead."
Bhagavad-gita 17-10 Purport
"It is not that Krsna is hungry and is begging food from us. The purpose of this offering is to create a loving transaction. Krsna wants this transaction: "You love Me, and I'll love you." As God, Krsna's energy creates and sustains everything, so why should he beg a leaf, a fruit and a little water from us? He will be very pleased, however, if we offer him a piece of fruit, a leaf and water with love, saying, "Krsna, I am so poor that I cannot secure anything. I have secured this fruit and a leaf. Kindly accept them." Such an offering would make Krsna very glad. If He eats what we offer, our life will be successful, for we will actually make friends with Krsna. Fruit, flowers and water can be secured practically in any part of the world by any man, poor or rich, and can be offered. We should remember then that it is not vegetarianism which is important, nor is it that God is in need of anything. The important point is that we simply have to try to learn how to love Krsna.
Love begins with this give and take. We give something to our lover, he gives something to us, and in this way love develops. When we create any loving transaction with any boy or girl, man or woman, we give and take. Thus Krsna is teaching us how to give and take. Krsna is begging us: "Try to love Me. Learn how to love Me. Offer something to Me."
Matchless Gift, Chapter 3
"Actually, giving up meat-eating is not a question of Krsna consciousness but of civilized human life. God has given human society so many things to eat--nice fruits, vegetables, grain, and first-class milk. From milk one can prepare hundreds of nutritious foods, but no one knows the art. Instead, people maintain big slaughterhouses and eat meat. They are not even civilized. When man is uncivilized, he kills poor animals and eats them.
Civilized men know the art of preparing nutritious foods from milk. For instance, on our New Vrndavana farm in West Virginia, we make hundreds of first-class preparations from milk. Whenever visitors come, they are astonished that from milk such nice foods can be prepared. The blood of the cow is very nutritious, but civilized men utilize it in the form of milk. Milk is nothing but cow's blood transformed. You can make milk into so many things--yogurt, curd, ghee (clarified butter), and so on--and by combining these milk products with grains, fruits, and vegetables, you can make hundreds of preparations. This is civilized life--not directly killing an animal and eating its flesh. The innocent cow is simply eating grass given by God and supplying milk, which you can live on. Do you think cutting the cow's throat and eating its flesh is civilized?"
Science of Self-Realization, Chapter 1
"All these cities and villages are flourishing in all respects because the herbs and grains are in abundance, the trees are full of fruits, the rivers are flowing, the hills are full of minerals and the oceans full of wealth. And this is all due to Your glancing over them.
Purport: Human prosperity flourishes by natural gifts and not by gigantic industrial enterprises. The gigantic industrial enterprises are products of a godless civilization, and they cause the destruction of the noble aims of human life. The more we go on increasing such troublesome industries to squeeze out the vital energy of the human being, the more there will be unrest and dissatisfaction of the people in general, although a few only can live lavishly by exploitation. The natural gifts such as grains and vegetables, fruits, rivers, the hills of jewels and minerals, and the seas full of pearls are supplied by the order of the Supreme, and as He desires, material nature produces them in abundance or restricts them at times. The natural law is that the human being may take advantage of these godly gifts by nature and satisfactorily flourish on them without being captivated by the exploitative motive of lording it over material nature. The more we attempt to exploit material nature according to our whims of enjoyment, the more we shall become entrapped by the reaction of such exploitative attempts. If we have sufficient grains, fruits, vegetables and herbs, then what is the necessity of running a slaughterhouse and killing poor animals? A man need not kill an animal if he has sufficient grains and vegetables to eat. The flow of river waters fertilizes the fields, and there is more than what we need. Minerals are produced in the hills, and the jewels in the ocean. If the human civilization has sufficient grains, minerals, jewels, water, milk, etc., then why should it hanker after terrible industrial enterprises at the cost of the labor of some unfortunate men? But all these natural gifts are dependent on the mercy of the Lord. What we need, therefore, is to be obedient to the laws of the Lord and achieve the perfection of human life by devotional service. "
Srimad-Bhagavatam 1:8:40 Purport
Bhaktivedanta Book Trust. HDG A.C. Bhaktivedanta Swami Srila Prabhupada.