A “sequence” is a Latin hymn, usually in prose, to be sung with the “Alleluia” before the reading of the Gospel. This translation was published in my Advent and Christmas collection Run, Shepherds, Run (Morehouse, 2005), pp. 39-40 and appears here in a slightly revised form. The original Latin text may be found in The Oxford Book of Medieval Latin Verse (Clarendon Press, 1959) pp. 133-34.