What icon is this?
This is a picture of Andrei Rublev's icon of the Trinity, originally written in the 15th century. A larger version hangs in the offices of Trinity Integrative Medicine. The original is located in the Tretyakov Gallery in Moscow, Russia.

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What is the meaning of the Icon?
In the words of Henri J. M. Nouwen (writer of Behold the Beauty of the Lord: Praying with Icons), this icon depicts three angels, representing the Father, Jesus Christ and the Holy Spirit, inviting individuals to participate in their work in the world  .  .  .  offering hope to the world. This imagery comes from the story of the visit of three angels to Abraham, recounted in Genesis 18:1-8 - lending an alternate title to this work: The Hospitality of Abraham.