"Give to the one who asks of you, and do not turn your back on one who wants to borrow." As he continues with his  "new teaching," Jesus gives an instruction that seems not to have been totally alien to his immediate audience. As a matter of fact, the instruction not to turn one’s back on an individual who is seeking a favor is reminiscent of, and captures the spirit of a number of the six hundred plus laws that the Israelites were to observe. More importantly, it is a reflection of the covenant God made with Abraham, and indeed with all humanity. For God told Abraham that God was blessing him so that he in turn could become a  blessing to others. It is a command about which God continues to remind God's people over and over again: they are required to be good to one another and especially to the least fortunate because God has been good to them (cf. Exodus 22:21; Deuteronomy 5:15; 15:15; 16:12). Consequently, we might become hesitant to identify the instruction as a new teaching. However, Jesus gives the instruction as a conclusion to his take on the retaliation law,  ‘An eye for an eye and a tooth for a tooth.’ Understood in this context, the instruction takes on a new meaning and becomes a new teaching.
The Old Testament command on retaliation (cf. Leviticus 24:20) was meant to moderate vengeance and ensure commensurate retribution in order to foster peace and harmony amongst the people. According to Jesus, however, peace and order/harmony in a community should not be founded on retribution (no matter how fair it is) or upon fear of revenge. Instead, peace and harmony should result from the members of the community embracing the virtue of charity and making it their mainstay. A community in which men and women live charitable and unselfish lives will have no need for a law governing retribution, for any act of transgression, should any arise, will be easily dealt with through forgiveness and understanding. It is along this line that I tend to understand Jesus’ instruction on reaching out and helping someone in need. 
Refraining from retaliation is a demonstration of selflessness and an invitation to the other to learn to put the interest of others before his/her very own. Refusing to embrace the law of retaliation (an eye for an eye and a tooth for a tooth) is the most practical way of living out the Christian call to charity.