You shall have the same rule for the sojourner and for the native, for I am the Lord your God.
Social justice as it pertains to the government is a matter of that government applying the same objective, universally binding laws on all of society - regardless of ethnicity, wealth, socio-political status, or anything else that shows partiality.
Social justice is not a matter of the government coercively taking money from one group of citizens in order to give it to another group. That is theft. Likewise it is not redefining the definition of marriage in order to include a group of people who would otherwise be considered adulterous or fornicatory. That is bearing false witness. Neither is it allowing people to kill others on the basis of geographical location or alleged "property rights" (abortion). That is murder.
True social justice as far as the government is concerned in these circumstances would be for it to allow all citizens to reap what they sow in the economic marketplace, to leave the definition and institution of marriage as described in God's Word and to uphold all civil laws regarding adultery or fornication (in their various physical acts), and to punish all murderers regardless of the victim's location at the time of the murder.
I am not here advocating right now that the government enforce the stopping of all social welfare programs, or the punishment of all publicly practicing non-heterosexuals and adulterers as well as all abortion workers or advocates. There is no righteousness in enacting and enforcing ex post facto laws.
But I am saying that as the church reaches more people with the gospel of Jesus Christ, and more disciples of Christ bring every area of their lives into conformity with His will - then by way of passionate but humble persuasion and through the democratic-republic process of this country, the laws of this country will become more in line with the laws of God for any society (i.e. the perfect civil Law he has already revealed - Ps. 19:7).
Then, and only then, would it be attainable to stop all state-mandated social welfare programs as well as enact and enforce appropriate laws for all public forms of sexual perversion (adultery, homosexuality, incest, bestiality) and murders (including abortion). And that should be the goal.
As for helping the poor and doing what is right and noble in society, that is a matter for private citizens to do according to their own conscience (which people will do when they are won over by the Word of God, Acts 24:16; cf. 2 Cor. 1:12; 1 Tim. 1:5).
As it pertains to government though, true social justice is simply applying true civil justice - enforcing the same objective, universally binding laws on all of society regardless of ethnicity, wealth, socio-political status, or anything else that shows partiality. Social justice is not the government engaging in acts of charity, welfare, education, healthcare or anything else that is not a matter of civil justice.
You shall do no injustice in court.
You shall not be partial to the poor or defer to the great, but in righteousness shall you judge your neighbor.