Sword of the Spirit (Word of God): The sword is used to defend, justify and cut through all that rise up to oppose us in our walk with the Lord. The sword is also used for offensive tactics and strategies.
Here God is telling us that it is through our tongues we use the 'sword of the Spirit', which is his word,(Romans 13:4). "For the word of God is quick, and powerful, and sharper than any twoedged sword, piercing even to the dividing asunder of soul and spirit, and of the joints and marrow, and is a discerner of the thoughts and intents of the heart",(Hebrews 4:12). In ( Matthew 4:3-11) prior to Jesus ending his fast, satan came and tempted him. Just as he does us all. In this important event in the life of any believer, Jesus taught us how to defeat the accuser of the brethren, by quoting God's word to him and then rebuking him, v. 10. Satan did not leave until he got the idea that this man fights with the word of God and there's no getting through at this time. It took a few times, until he finally "left him". Most of the time he does not leave us immediately; but if you continue to "resist the devil" by using the word of God openly and verbally, "he will flee from you",(James 4:7). Also it is not in the time of confrontation that we are comforted; but rather when it is over and we have the victory then, "angels came and ministered unto him",v.11.
Our mouths are so powerful and to be used to "speak as the oracles of God",(1 Peter 4:11). We must use God's word in every aspect of our life's. If you are battling something, my suggestion is to go to the word of God find your particular problem in the scriptures and then proclaim those scriptures over that problem with authority and name of Jesus Christ pleading his blood over everything. There is nothing in God's word that cannot relate to whatever problem your in. We are to use the 'sword of the Spirit' in all areas of our life's at all times. There is another sword spoken of by King David and it is this sword that speaks "bitter words",(Psalm 64:3). This sword I was quite familiar with at one time; that is to say before the Lord saved me from my own self destruction. Usually anger, hurt and bitterness are the muscles used to thrust this sword of which David speaks of. God has given us his word, so that we may use it to our benefit, his purpose and the glorifying of our Lord Jesus Christ in all things,(1 Peter 4:11). So please read God's word with a receptive heart, pray that God will fill your mouth with his word and remember when under attack only by the word of God will you prevail with victory everytime!