Salt -Colossians 4

Col 4:6 Let your speech always be with grace, as though seasoned with salt, so that you will know how you should respond to each person. Salt is what makes the taste complete. Grace is what makes a person's life complete. Grace is to see a person in God's eyes, not our own eyes. When we look at someone, it's easy to just look at the outside, and place judgement according to what we see. And that's incomplete and not fair to that person. When we pray for someone, God will give us wisdom and insight as to how He sees that person, and that's grace, and without this grace, the taste has got something missing.
For example, if we see Rehab, it's very easy and likely that we'll just see her as a sinner, a gentile, a prostitute, but if we see her with grace, she'd be one of the bloodline descendant of Abraham, that leads to Jesus. What a difference that will make! Without the salt, her life will be so incomplete.