Twenty-eight years ago this week, St. Stephen's Church in south Minneapolis opened an overnight "Emergency Shelter" for homeless people in the basement of the priests' residence. The parish dared to believe the nation would not long tolerate the indignity visited on the poor of this nation following on Ronald Reagan's presidential election one year earlier. After some years it reluctantly removed the word "Emergency" from the shelter's name. It has been receiving guests nightly since Dec. 8, 1981. In 1976 the National Catholic Reporter newspaper invited a number of prominent American Catholics to submit a message to the nation on its 200th birthday, in less than 150 words. Dorothy Day, cofounder of the Catholic Worker movement, used but one word: "Repent." This nation and its leaders (political, business, civic and religious) need to hear that message again. The tolerance of poverty in this nation is a mortal sin. In the Christian community, we are in the midst of the Advent season where we meet John the Baptist crying out that same message: "Repent." EDWARD FLAHAVAN, ST. PAUL. FORMER PASTOR, ST. STEPHEN'S CHURCH, MINNEAPOLIS