Twice in the Gospel of Matthew Jesus quotes Hosea 6:6 to the Pharisees, “I desire mercy and not sacrifice” (9:13 and 12:7). The full quote from Hosea goes like this:
For I desire mercy and not sacrifice,
the knowledge of God rather than burnt offerings.
In the context of the prophecy of Hosea, the knowledge of God does not refer to merely a mental or even a heart knowledge. The knowledge of God is a reference to an intimate marital relationship with God. Earlier in Hosea (2:20), God defines this knowledge:
I will betroth you to myself in faithfulness,
And you shall know the Lord.
Moreover, throughout Hosea the fault of God’s people, the fault of Ephraim and Judah, is that they have gone “whoring” and committed “harlotry” with vanity (the worthless idols of the world around them). Even the marriage of the prophet Hosea himself points to what it means to know, or not to know, the Lord. Hosea’s unfaithful wife turns (again) to harlotry, yet he persues her and “buys” her back. He is willing to know her, but she is unwilling to know him.
In marriage, intimacy is not merely a matter of a physical relationship, but it includes it. A wife (or husband) is unfaithful--no matter how much she protests that she truly loves her husband in her heart--if she has an intimate physical relationship with another person. A component of marital “knowledge” is physical faithfulness and loyalty. One cannot play the field: that’s not marriage, that’s whoredom, that’s idolatry.
In our relationship with God, our knowledge of God, our intimacy with God, also has a physical aspect. The worship of God involves not just our mind and heart, but also what we do. God has taught us through the Church how to love Him, what actions are appropriate, what actions say to God, “I love You.” The Church lays out for us a cycle of prayer, fasting rules, exhortations to give alms, all of which require physical action. These are the ways we are taught to worship, the ways we are taught to draw close to God. To pray you have to attend services and actually say prayers. To fast you have to eat or not eat certain foods (or, importantly, amounts of food). To give alms you have to work hard to make a buck, and then you have to give it away. And there are more, all things you have to do. These are part of knowing God, the physical aspect of our loving intimacy with God.
However, you can do all of the actions correctly and zealously and still fail to find intimacy. I have known couples who have divorced not because the physical aspect of their relationship was not working out, but because it was working out by rote. God does not ask for right technique or perfect performance, God asks for love. God’s first and greatest commandment is to love Him with all our hearts, minds and bodies.* The end of the physical relationship in marriage, and in our relationship with God, is intimacy. Our Christian goal is to know the Lord, to become “one flesh” with Him. And while the physical aspects of our relationship with God are important, they are the means to an end, they are the means by which we are transformed (heart, mind and body) into the Bride of Christ. Without a heart and mind fully committed to and being transformed by Christ, we may find ourselves hearing the same words Jesus spoke to the Pharisees, “Go and learn what this means, ‘I desire mercy and not sacrifice.’”
*Note that in the various versions of the greatest commandment, sometimes the word “soul” (as in “life”) and sometimes “strength,” and sometimes both are used as a reference to the physical aspect of the triad, mind, heart, body.