Here's the d'var Torah I wrote for this week's portion in 2006 for the now-defunct blog Radical Torah.
Much energy and imagination have been devoted to the question of why the aseret dibrot, the utterances given at Sinai, are followed by the instruction to make altars out of earth or whole stone, not stone which has been cut.
In his commentary on the phrase "an altar of earth," Rashi writes, "the altar must be attached to the ground; it should not be built on columns or some other foundation." In other words, the altar -- our mode of communication with God, according to the understanding of that time -- must be rooted in the earth. God is commanding us to "ground" ourselves. And on the matter of uncut stones, the usual explanation is that metal implements suggest or imply swords, which shorten or curtail life -- an action in direct opposition to the enlivening altar. (Well, enlivening for us; not so much for the animals being sacrificed. But we'll let that go.)
The real point of Exodus 20:22 is how to approach and connect with God. And there's much to learn here, even (or especially) in this post-sacrificial age.
"Rabbi Berakhya and Rabbi Helbo taught, in the name of Rabbi Shmuel son of Nahman: (Man) was created from the place of his atonement, as it is written (Shemot 20), "An altar of earth shall you make for Me". The Holy One said: I shall create him from the place of his atonement; would that he will live." (Bereshit Rabbah, 14:8)
Let's unpack that: our place of origin, the earth which nurtures and nourishes us, is the place of our atonement. Torah instructs us to make an altar out of the very substance from which, Torah tells us, we were formed. Our ascent toward God, our locus of holiness, must be made of the same stuff as we.
What makes this injunction most powerful is that it comes on the heels of the revelation at Sinai, arguably the most transcendent experience imaginable. Thunder! Celestial fireworks! A voice from the heavens! This is the pinnacle of religious experience, a direct moment of contact with God at God's most transcendent. Torah immediately moderates that story with a reminder that God is immanent in creation, too. And it is incumbent upon we creatures of the earth to connect with God using the earth in which we're planted and from which we live.
One line of traditional commentary interprets the "altar of earth" to mean the land of Israel. It's a pretty notion, but a problematic one for Diaspora Jews who value the post-exilic understanding that we can reach God from anywhere. Allow me, therefore, to offer a Diaspora-friendly alternate version of that teaching. Just as we find in every sanctified Shabbat a temporal equivalent to the spatial holiness the Temple once provided, maybe our many spaces and places of study and prayer make of the entire earth an altar.
In that case, the prohibition against wielding sword on stone becomes a powerful exhortation to relinquish the weapons we use on each other and on our planet. If we are serious about reaching out to God, then we mustn't wield our swords on the altar-place where that connection happens...and if the whole earth is our altar-place, then it's time to turn our weapons into plowshares. Because there is no place devoid of God's presence, and our implements of destruction profane places that would otherwise be holy.
Today in lieu of bulls and sheep we offer words and intentions to God. The instruction to make an altar of earth or whole stones tells me that we need to bring our prayers and our mindfulness in a way that's whole and grounded in all that we are. Today our altar of earth is everywhere we live and everywhere we go, and the whole stones that build our places of ascension are the whole and holy constructions of our hearts.