This idiom is used to introduce a special message from God. Alternate translation: "Yahweh gave a message to Zechariah. He said, 'Yahweh" or "Yahweh spoke this message to Zechariah: 'Yahweh" (See: [[rc://en/ta/man/translate/figs-idiom]])
The abstract nouns "justice," "faithfulness," and "mercy" can be stated as adjectives. Alternate translation: "When you judge, be just, faithful to the covenant, and merciful" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])