The word batter also connotes the image of the walls or gates of a city, village or town being charged with a large piece of wood called a ram for the purpose of breaking down the walls and entering the city or town . With this being said, he is asking for his heart to taken over forcefully and violently by the three-personed God. The three-personed God refers to the trinity, which are God, Jesus and the Holy Ghost. Therefore, "batter my heart" is a metaphor for the heart as it is compared to the city. Furthermore, when this line is coupled with line two "for You/ as yet but knock, breathe, shine and seek to mend" these actions are subtle and gentle, insinuating that God is exceptionally kind and caring to the individual. To mend is to make (something broken, worn, torn, or otherwise damaged) whole, sound or usable by repairing it, but these actions are not enough for the speaker. He feels as if his heart needs to be awakened aggressively by the three-personed God, and discusses this in lines three through four.
Line three continues to discuss the violent awakening for which he is asking "that I may rise and stand, o'erthrow me and bend." That I may rise and stand connotes that the speaker feels as if he is bent over with some weight or burden. To o'erthrow is the action of overthrowing something; the fact of being overthrown; defeat; deposition from power; destruction, ruin; an instance of this. This implies that the speaker wants to recognize God's power, but he worries that the only way God will get through to him is by doing something violent and completely overthrowing his life. To bend means to force (an object, especially a long or thin one) from a straight form into a curved or angular one, or from a curved or angular form into some different form. Referring back to the beginning of line three, "that I may rise and stand" suggests that the speaker is bent but is asking to straighten from his current state.
