Boaz' role was that of "kinsman-redeemer" (Ruth 2:20, Ruth 3:12).  The same word is translated "avenger."  It refers to a relative of an impoverished or murdered Israelite, who undertook either the buying of his property or the exaction of revenge upon the perpetrator (Num 35).  In Exodus, the term is used to refer to God delivering Israel from Egypt (Ex 6:6, Ex 15:13).  In Leviticus, it refers to land or a house, or even selling oneself into servitude (Lev 25):  all these may be bought back by the original owner or a kinsman or, failing those remedies, they were restored at the year of Jubilee.  In Isaiah, the term is applied to the Lord, who redeems Jacob from Babylon and from sin (Isa 41:14, Isa 43:14, Isa 44:22, Isa 48:20, Isa 59:20, Isa 62:12).

          

Justice in the Old Testament was not impersonal or bureaucratic.  It was community- and family-focused.  But on the other hand, it was not random and variable.  God set the standards universally, but they were applied and upheld locally through the extended family units.  This promoted unity in the clan, accountability, mutual support.  It avoided the sterile cliches of modern egalitarianism  -- where the state imposes a forced and false equality of life -- and required that the more prosperous members of the family should extend practical help to those undergoing hardship.  There is a wonderful parallelism between God's application of this term to Himself in His treatment of Israel, and the conduct He expects from Israelites to each other.  In this sense, Boaz is legitimately seen as a "type" of God Himself.  We also see God's "bias" towards freedom.  In all the unfortunate vicissitudes of life which an Israelite could experience -- unexpected death, financial loss, crop failures, lack of heirs -- God provided alternative sources of help.  One was never at a dead end, never bankrupt, hopeless or helpless.  Even in utter poverty, one had a legal claim upon more well-to-do relatives for sustenance, restoration, and even progeny!