But, the stories do have a similar trajectory, which might make it fun to weave them together in a sermon. Both start in a very particular time and place, in both stories the Divine speaks words that beckon, and both feature protagonists who declare their unworthiness before God but follow anyway.
If, on the other hand, you're taking your sermon in an evangelism direction, rather than a call direction, you might want to consider Ann Svennungsen's words, as quoted by Kate Huey: "The calling is not to hook people and drag them in," Svennungsen writes: "It is rather to cast the net of God's love all around--open to all the world--and then wait with patience for the Spirit's work and to see if any are caught by God's vision and grace."
Are you preaching on psalms instead? Continuing your series on Corinthians? Or veering off the lectionary course altogether? (By the way, if you are considering moving off lectionary, this new discussion over at Working Preacher has just come to my attention).
Let us know in the comments. We look forward to hearing from you!