"And thou shalt make an altar of shittim wood, five cubits long, and five cubits broad; the altar shall be foursquare; and the height thereof shall be three cubits." (Exodus 27 v 1)
The word altar in the Hebrew language means "a slaughter place." In the Greek, it's called "a place of sacrifice." The spiritual altar is the place where natural, spiritual, earthly things that hinder your walk with God are consumed by the fire of God. In essence It is the place where you become a living sacrifice.
Each believer are a priest unto God. A member of the royal priesthood of Jesus Christ. Therefore you have to continously wash and undergo the fire of consecration to qualify you for ministry. This is where you prove the new ideals and attitude, by laying down your life to embrace God's perfect will. Everything within you that does not line up with God's perfect will comes to an end at the altar. They are set on fire and consumed in the Spirit.
What do I mean by set on fire and consumed in the Spirit? This terminology describes what it would feel like after you become committed to a life of prayer, when the Lord allows you to be confronted with certain situations that will become the very trying of your faith. You must always remember that once you confess and declare that you believe the works of Jesus Christ and what He has done in your life, then every work of the Lord in your life shall be tried by fire. Some works are made of straw, and others are made of wood, but only that which endures the fire will qualify to be used of God.
For example, gold jewelry is forged by being placed in the fire. The goldsmith's purpose for doing this is to draw the impurities and black tar particles to the surface. Then he pulls the gold out of the fire, scrapes off the impurities and foreign particles, and puts it back into the fire. He does this repeatedly until he's finished with the deepest interior of that lump of gold. During this process, everything that would cause this piece of jewelry not to shine, not to be declared as costly pure gold, is burnwed to increase its value.
God is doing this same purifying work in our lives. When we allow God to put us "in the fire" (in fiery situations), we are co-operating with everything He is doing in us. We are releasing every impurity that would hinder us from becoming a most valuable resource to Him and to His work. When these impurities are burned out of us, nothing in prayer can be hindered - because the forging process strengthens us in the Spirit. This makes us valuable instruments in God's hands.