In a revised edition of this catechism, there is a different answer given to this question. I’ve given that one in the first comment on this post and I hope you’ll tell me which answer you think is better.
Part III: Questions about Salvation
93. Q. What is righteousness?
A. It is God’s goodness as revealed in his law, and as honored in Christ’s perfect obedience to that law.
(Click through to read scriptural proof.)
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And he said, “I will make all my goodness pass before you and will proclaim before you my name ‘The LORD.’ And I will be gracious to whom I will be gracious, and will show mercy on whom I will show mercy.
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The LORD passed before him and proclaimed, “The LORD, the LORD, a God merciful and gracious, slow to anger, and abounding in steadfast love and faithfulness…
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He loves righteousness and justice;
the earth is full of the steadfast love of the LORD.
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Afterward the children of Israel shall return and seek the LORD their God, and David their king, and they shall come in fear to the LORD and to his goodness in the latter days.
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Note then the kindness and the severity of God: severity toward those who have fallen, but God’s kindness to you, provided you continue in his kindness. Otherwise you too will be cut off.