Possible theme(s): Only One Thing Needed or Christ Alone
You O Lord are my strength and my shield; my heart trusts in you and I am helped; therefore my heart dances for joy, and in my song I will praise you. (Psalm 28:8)
Let us not serve you grudgingly like slaves,
But with the gladness of children
Who delight in You
And rejoice in your work
Empowered by the Spirit of Jesus Christ. Amen.
Abraham and Sarah offer hospitality to three strangers.
The providing of hospitality is the common theme with the gospel reading today. Abraham directs Sarah what to do. (By the standards of the day and the location) a sumptuous meal is provided. Abraham is mostly exhibiting a cultural norm of being hospitable. But we can see an element of grace: Abraham welcomes three men with no particular claim on him through family or other ties. Without obligation to do so, the men indicate that Sarah will (finally) become pregnant with the child promised of God.
In entertaining strangers, Abraham and Sarah have welcomed angels (see also Hebrews 13;2). We may even say, stretching a theological bow from the Old Testament to Trinitarian orthodoxy, they have welcomed God in Three Persons. Google "Rublev's Icon" for a perfect, profound illustration of this Trinitarian meal!
The perfectly formed Christian character finds its description in this psalm! Note that this character includes both personal piety and integrity, social relationships, and community dealings.
That this psalm is a psalm (a song for worship) is justified by the opening verse: the perfectly formed Christian character is not a list of moral attributes but a description of the person who may live in the close presence and intimacy of God.
Paul is "all Christ" in this passage as he sets out his understanding of the significance of Jesus of Nazareth. There are various ways in which we could break his praise-poem (doxology) of Jesus Christ into categories.
One way is Christ the creator (vss. 15-17), Christ the head of the church (vss. 18-22), Christ in the life of the believer (vss. 23-28).
Another way is to think of vss. 15-22 as a creed, this is what Christians believe about Jesus Christ, and vss. 23-28 as code of discipleship, this is how Christians live out the gospel. A sermon along these lines might reflect on the significant development in roughly 30 years, between the initial understanding of Jesus as a carpenter from Nazareth who performed miracles and taught as other rabbis of his day did (c. 30 AD) and this christological exposition of Christ as the fullness of God (c. 62 AD).
A third division could be to think about what is said here about the gospel: Jesus as the centre of the gospel message Paul proclaims, the content of the gospel (especially vss. 20-22), and the aim of the gospel (especially vss. 27-38).
Nevertheless the passage flows from one verse to another, each of which has 'deep content' about important matters in the life and belief of Christian people. Whole sermons could be preached on verses such as 15, 16, 17, 18, and, well, each of the other individual verses!
Mary and Martha are enigmatic characters in the gospel, appearing twice only: here as a pair of sisters and, in association with their brother Lazarus, in John's Gospel. Luke almost certainly tells us this story to illustrate aspects of discipleship.
As a follow up to the parable of the Good Samaritan, the story is an illustration of loving God and loving your neighbour, the story of Mary and Martha illustrates love of God (through Mary's devotion to Jesus as her Lord) and love of neighbour (Martha's practical service). In respect of discipleship alone, the story illustrates the priority of the disciple: to sit at the feet of the master teacher, learning as much as possible, even prioritizing this over the ordinary work of life. Typically of Luke, this story underlines that female disciples are important in the kingdom of God (see also Luke 8:1-3).