Teacher, what is the greatest commandment of all?
Jesus replied..."There is one and only one commandment above all, and by it you can create a gateway, a litmus test as it were, whereby you can test every person, every belief, every priority of life, faith, and order in the community. This one commandment provides for you a theme and an issue by which, within your own faculties of judgment, you can measure and thereby approve or reject every person, every believer, every pastor, yea even every judge, every appointed and elected official of the government or leader of any organization. By this one thing you can discern the rightness and the priority of every practice of faith, of church order, of mission, even beyond your church to the policies and laws of the society at large. With this one thing you will have the discernment to consider, choose, and judge not only the belief and practice of your family and your local congregation and of the faith group within which you worship, but also all families and all churches and faith groups, yes even all governments and leaders at all levels. If they do not align with this one issue, then they shall be deemed unworthy of any association with you and those in agreement with you in this singularly righteous cause."
In reality, that is not what Jesus said. This is a conversation that we might have spoken, in our self-assured confidence and our tendency to judge others. But it is not the response spoken by Jesus. Jesus' response, recorded in three gospels and consistent with the oldest expressions of biblical faith, was ...
'Hear O Israel! The Lord our God is one Lord; and you shall love the Lord your God with all your heart, and with all your soul, and with all your mind, and with all your strength.' The second is this, 'You shall love your neighbor as yourself.' There is no other commandment greater than these."
I don't advocate a "single issue" ethical or political perspective. And for sure I do not advocate any single issue or principle of my faith as a litmus test or basis of judgment of the leaders and complex authority structures and ethical / legal principles of society at large. But if there is a single issue, principle, or theme, it would have to be love, as in the Old Testament chesed (mercy, loving-kindness) and in the New Testament, agape (sacrificial or unconditional love or charity). Love - the care and concern for the health and well-being of fellow humans - is an appropriate lens through which to evaluate the fitness of those who would aspire to leadership and the appropriateness of the various laws and policies that give goodness, structure and order to our society.
Notes:
This encounter or similar exchanges is found in the New Testament passages:
Matthew 22:35-40; Mark 12:28-31; Luke 10:25-28; John 13:31-35
Note that the Luke passage is followed immediately (and by way of interpretation) by the story of "The Good Samaritan," in Luke 10:29-37 as the inquiring person asked "Who is my neighbor?"
These passages reference or echo the Old Testament passages Deuteronomy 6:4-5 and Leviticus 19:18. The Leviticus reference (love your neighbor) may be considered more obscure and did not enjoy nearly the status of the famous Deuteronomy "Shema" passage (below) prior to Jesus' teaching in this instance, elevating the importance of selfless love toward others.
Deuteronomy 6:4-5 - "Hear, O Israel! The Lord is our God, the Lord is one! And you shall love the Lord your God with all your heart and with all your soul and with all your might..."
Leviticus 18:18 - "You shall not take vengeance, nor bear any grudge against the sons of your people, but you shall love our neighbor as yourself; I am the Lord."