I Kings 19:16, 19-21; Psalm 16:1-2, 5, 7-8, 9-10, 11; Galatians 5:1, 13-18; Luke 9:51-62
The first reading and the Gospel this Sunday both present the demands of God's call in seemingly very stark and absolute terms. In the first Book of Kings, Elisha apparently must immediately drop everything, his whole life and family, in order to follow Elijah. In the Gospel, we hear Jesus saying, "Let the dead bury their dead," and telling someone who wishes to stop to say good-bye to his family, "No one who sets a hand to the plow and looks to what is left behind is fit for the kingdom of God."
This could be interpreted as something very harsh and unforgiving. However, obviously we know that Jesus precisely brings a message of mercy available to all who repent of their sins, so perhaps this passage should not be taken in the most absolute and literal way possible. A further indication of this is that the Church does not urge us to ignore bonds of human love and family, or reject traditions of respect for the dead. On the contrary, the Church herself enters into and upholds these realities as part of the faithful following of Christ.
Furthermore, in other places in the Gospel it is clear that Jesus felt particular compassion for those suffering loss of their family and loved ones. In particular, we can see in John 11 that Jesus was deeply troubled by the sorrow of Martha and Mary at the death of their brother Lazarus. Before raising Lazarus from the dead, Jesus did not warn Martha and Mary against looking to what was left behind. Indeed, Jesus Himself wept at the tomb of Lazarus.
Above all, when facing His own death, and the time of the fulfillment of His mission, some of Christ's last words were to John concerning Mary: "Behold thy mother." What is often emphasized in this passage (and quite rightly) is the broad sense of these words, as placing the whole Church under the motherhood of Mary. However, more specifically Jesus is surely also fulfilling His love for his mother in a human way, calling upon his beloved disciple John to take the responsibility in love of serving as a son to Mary in her life.
The second reading, from Galatians, begins with the theme of exodus, specifically our exodus from sin. This echoes the original story of the Exodus of the Israelites out of Egypt, when the Lord freed them from slavery. However, the Israelites more than once fall into looking to what is left behind, longing for a return to their former slavery among the Egyptians, which symbolizes turning back to a state of sin. Paul exhorts Christians not to fall into this trap: "For freedom Christ set us free; so stand firm and do not submit again to the yoke of slavery. For you were called for freedom, brothers and sisters. But do not use this freedom as an opportunity for the flesh; rather, serve one another through love."
Thus, what should be "left behind" when one sets one's hand to the plow as a Christian is not fundamentally family or friends, though such sacrifices may sometimes be necessary, but rather the slavery of sin. This does not mean, of course, that we can simply ignore the challenging words of the Gospel, imagining that the call of Jesus does not require us to approach life in a fundamentally different way. These passages push us to recognize the ultimate self-surrender that is intrinsic to the following of Christ. This total self-surrender in love is something each person is called to in some way, shape or form, in each person's specific calling.

