The angel of Yahweh appeared to him, and said to him, Yahweh is with you, you mighty man of valor.
Now, Gideon's dad was an idolater. Gideon's dad had his own place of worship, a grove with the altar of Baal or an idol of Baal there where they worshipped in the grove. And so God says "Now take a second bullock, make another altar, cut down the grove that your father has his place of worship. Throw down the altar of Baal, build an altar unto God and offer the second bullock using the wood of this grove as the fire and all."