Genesis 12:7, [Abram] built [at Moreh] an altar to the LORD, who had appeared to him.
This was the first time Abram built an altar to YHWH, and he did not pick it at random; God Himself chose the location. And for what purpose? In Luther’s words, “He appoints a definite place where the church should come together to hear the Word of God, offer prayers, praise God, and bring sacrifices to God; for this is what it means to build an altar” (from Lectures on Genesis, Luther’s Works 2:284-285). This is why we have altars in our churches. Church is God’s chosen means for His people to commune in fellowship and praise Him. What sacrifices do we bring before our altars today? As a royal priesthood and a holy nation (1 Peter 2:9), we offer intercessory prayers to God. Ultimately, the altar is where God’s promise is proclaimed. It is proclaimed in His Word through the Gospel, tasted in Christ’s body and blood in the Lord’s Supper for forgiveness of sins, and the cleansing of our guilt in Baptism.