The Catholic Herald is pleased to bring readers this essay by Fr Hugh Somerville Knapman OSB, closely adapted from his 2018 book, The Ecumenism of Blood: Heavenly Hope for Earthly Communion (Paulist Press, 2018. New York / Mahwah, NJ), to lead the Week of Prayer for Christian Unity, 2021.The Week of Prayer for Christian Unity runs each year from 18-25 January , beginning with the traditional Feast of the Chair of St. Peter and running through First Vespers of the Conversion of St. Paul the Apostle. The Servant of God, Fr. Paul Wattson -- convert and founder of the Franciscan Friars of the Atonement -- first proposed the dates as a fitting time in which to call all Christians to ecumenical fellowship. The theme of this year's recurrence, "Abide in my love and you shall bear much fruit," is taken from the Holy Gospel according to St. John (15:5-9).On several occasions, publicly though not systematically, Pope Francis has spoken of the “ecumenism of blood.” He has done so in response to alarming reports of Christians – Catholic and non-Catholic – being killed for their Christianity, especially in the Middle East. His use of the term grew more emphatic after the 2015 murder of Coptic Christians in Libya, though he had first used it more than a year before their deaths.In December 2013, responding to a question regarding the priority of ecumenism from Andrea Tornielli, who was then the Vatican correspondent for the Italian newspaper, La Stampa, Pope Francis said: