and build an altar to Yahweh your God on the top of this stronghold, in the orderly manner, and take the second bull, and offer a burnt offering with the wood of the Asherah which you shall cut down.
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."