The love of neighbor and love of God are not two distinct precepts, but two ways of the one precept of charity:
The love of God expands in love of neighbor. It would be mistaken to love God and not to love the neighbor.
Love of neighbor
The same Jesus in the Last Supper discourse insists on love of neighbor presenting it as the "new" commandment. Love of neighbor in fact, there has always been, both in the Jewish world, but out of it: the love of neighbor is rooted in man's very nature, so it is something natural and therefore universal. How then they can present Jesus as the "new", "his" commandment?
For the pagans the most excellent form of love of neighbor was in friendship mail. The friendship would be a mutual love between two persons, based on a commonality not only of nature, but of attitudes and, above all, of aspirations, commonality for which each is able to give and receive the benefit. This giving and receiving is a result of friendship, but it is not the constitution, which is friendship dowry is disinterest. So this love is benevolence and not of concupiscence, which arises from natural and non-calculating sentiment.
The most excellent form of friendship is based on mutual participation of spiritual goods, science and virtue. Certainly, this is a very noble and lofty conception of the relationship between men. It is found in the speculation of many philosophers, ancient, from Aristotle to the Stoics, Cicero. The expressions that define the friend as alter ego (another self) and how dimidiurn animae meae (half my life), suggestively express what they thought about the pagans.
Even the holy books praising the friendship. In Ecclesiastico warns against false friendship and enhances true friendship: "Who finds a faithful friend has found a treasure. Nothing can be compared, and it is not worth all the gold in the world to be put in balance with sake of his loyalty. He is balm of life and immortality...".
Jesus himself embodies that friendship excellence when, in the last supper, use the sweet friend nickname for his apostles: "do not call you servants, I call you friends .., you are my friends ... ". But the friendship of which Jesus speaks is something new to be found, and we lose together, in the new concept of charity, becoming brotherly love: the "Filia" becomes "philadelphia" according to St. Paul's terminology and St . Peter. The foundation is no longer equality of skills or inclinations of the individual, but it is a deeper equality in participation in the divine sonship, hence the human brotherhood, as we have already seen.
Jewish law, by the commandment of love of God, puts to love of neighbor: but the next is essentially intended as a compatriot: the Jew’s neighbor is the one who is part of God's people: are the next Israel. This is the sense of the precept formulated in Leviticus: "You shall love your neighbor as yourself". As part of the Jewish people the Scripture calls for an attitude of understanding and mercy. Mercy for the meanest: the call to care for the poor, the weak, the helpless, is like a note that echoes through all the books of the Old Testament.
On the mouth of the prophets it turns very often in harsh rebuke and reproach for those who are hard of heart and exploit the misery of others. The works that are contrary to these works are all pleasing to God and will attract the benevolent gaze: "never turning your face to any poor, and so it shall be, even the face of the Lord will turn from you" (Tobit 4: 7): mercy to the poor and wretched of Yahweh, compassion towards all the faithful of Yahweh. This compassion should go so far as to renounce the just vengeance: "do not seek revenge and do not store the insults of your fellow citizens in memory" (Lev. 19, 18); "Do not say, as he did to me so I will do to him, I will give to everyone according to what he has done" (Prov. 24, 29). Not only do not take revenge, but even retain hatred in his heart, "not hate your brother in your heart".
(Lev. 19, 17).
Are invitations to a much higher perfection, although in fact the usual criteria of behavior, in the case of offenses and insults, was limited to moderation, namely that revenge must not be greater offense: "eye for eye, tooth for tooth, etc.".
The latter criterion, as quantitative and outside, is certainly far more precise and easier to observe, not the criterion of renunciation of revenge and to completely interior renunciation of hatred. You understand that the zealous of the law, the Pharisees, were crowded leave aside these and insist on that for foreigners as guests.
As foreigners, they are assimilated willingly to the poor, orphans and widows to the weak short - to which, as now we have said, the law calls for indulgence and protection. They, too, will participate in the Sabbath rest also enjoy public holidays (Deut. 16, 14); Also they can glean and gather grapes and wine remain (Deut. 24: 19-21), etc. They also have the reproaches and the "woe!" against those who commit injustice to the detriment of foreigners (Deut. 27, 19; Jer. 22: 3-6). Leviticus even comes to recommend loving them: "If a stranger dwells in your land, do not oppress, but both of you as if it were a native of the country and love him as yourself".
The reason given to inculcate to the Hebrews this humane treatment toward the stranger is the memory of their Egyptian captivity: "remember that you were strangers in the land of Egypt" is a kind of restitution. However it is always only those foreigners who live in Palestine and are considered, not from the perspective of their nationality, but - as mentioned - of their civil status defenseless and exposed to arbitrariness. They considered not as strangers, but as wards.
As to foreigners as such, they are then considered as the nations, the Gentiles, in political and religious antithesis of God's people: the object of contempt and in a natural position of enemies of the chosen people. We must not forget that the whole history of Israel is a history of struggles against their neighbors to gain and retain Palestine in its political and religious independence. So the usual attitude and, almost, natural Jews against foreigners, was that of mistrust and hatred.
Even the pagans were proverbial hatred of the Jews against foreigners Tacitus, making common opinion echoed precisely detect their 'implacable hatred of all others. "Particularly the Pharisees, locked in their extreme nationalism, had to consider the hatred of enemies, strangers, nearly recognition of authentic Jewish card. So we understand how Jesus, wanting to present you with a clear highlight its new message, could oppose the new commandment, "Love your enemies", the ancient precept worded as "you shall love your neighbor and hate your enemy".
(Mt. 5, 43).