# But as for me

Here "me" refers to Micah, a true prophet, setting himself apart from the false prophets.

# I am full of power by the Spirit of Yahweh, and am full of justice and might

"the Spirit of Yahweh has given me power, justice, and might" or "the Spirit of Yahweh has enabled me to be strong, to declare what justice is, and to be mighty"

# to declare to Jacob his transgression, and to Israel his sin

"to declare to Jacob's descendants that they have broken Yahweh's law; I am telling the people of Israel that they have all sinned". Here "Jacob" and "Israel" are metonyms for Jacob's descendants. Micah uses both names to emphasize that all of his descendants are guilty of sin.