All Saints’ Day, All Hallows Day, or Hallowmas is solemnly celebrated on 1 November by many Western Liturgical Churches to honor, literally, all the saints, known and unknown; those individuals who have attained Heaven.
The saints are all the Holy men and women who have lived their lives for God and for his church, who now have attained Beatific vision and their reward of Heaven. In early Christian history it was usual to solemnize the anniversary of a Martyrs death for the Lord at the place of their martyrdom. Frequently there were multiple martyrs who would’ve suffered and died on the same day which led to multiple commemorations on the same day. Eventually,the numbers of martyrs became so great that it was impossible for a separate day to be assigned to each individually, but the church feeling that every martyr should be venerated, appointed a feast day to commemorate them all on the same day. At first, only Martyrs and St.John the Baptist were honoured with a special day but after a regular canonization had been established other saints were gradually also added and then were increased in number.
From Wikipedia: The origin of the festival of All Saints celebrated in the West dates to the month of May in the year 609 or 610, when Pope Boniface IV consecrated the Pantheon at Rome to the Blessed Virgin and all the martyrs. In the 730’s Pope Gregory III moved the Feast of All Saints to 1 November when he founded an oratory in St. Peter’s for the relics of the holy apostles and of all saints, martyrs and confessors, of all the just made perfect who are at rest throughout the world.”
Revelation 7:2-4, 9-14
I, John, saw another angel come up from the East, holding the seal of the living God. He cried out in a loud voice to the four angels who were given power to damage the land and the sea, “Do not damage the land or the sea or the trees
until we put the seal on the foreheads of the servants of our God.” I heard the number of those who had been marked with the seal, one hundred and forty-four thousand marked from every tribe of the children of Israel.
After this I had a vision of a great multitude, which no one could count, from every nation, race, people, and tongue. They stood before the throne and before the Lamb, wearing white robes and holding palm branches in their hands.
They cried out in a loud voice: “Salvation comes from our God, who is seated on the throne, and from the Lamb.”
All the angels stood around the throne and around the elders and the four living creatures. They prostrated themselves before the throne, worshiped God, and exclaimed:
“Amen. Blessing and glory, wisdom and thanksgiving, honor, power, and might be to our God forever and ever. Amen.”
Then one of the elders spoke up and said to me, “Who are these wearing white robes, and where did they come from?” I said to him, “My lord, you are the one who knows.” He said to me, “These are the ones who have survived the time of great
distress; they have washed their robes and made them white in the Blood of the Lamb.”
From the Book of Common Prayer, p. 194:
The Collect for All Saints’ Day
O Almighty God, who hast knit together thine elect in one communion and fellowship in the mystical body of they Son Christ our Lord: Grant us grace so to follow thy blessed saints in all virtuous and godly living, that we may come to those ineffable joys which thou has prepared for those who unfeigned love thee; through the same Jesus Christ our Lord, who with thee and the Holy Spirit liveth and reigneth, one God, in glory everlasting, Amen.
Hymn: For All the Saints
Text: William W. How, 1823-1897
Music: Ralph Vaughan Williams, 1872-1958
For all the saints, who from their labors rest,who thee by faith before the world confessed,thy name, O Jesus, be forever blest.Alleluia, Alleluia! Thou wast their rock, their fortress, and their might;thou Lord, their captain in the well-fought fight;thou in the darkness drear, their one true light.Alleluia, Alleluia! O may thy soldiers, faithful, true, and bold,fight as the saints who nobly fought of old,and win with them the victor’s crown of gold.Alleluia, Alleluia! O blest communion, fellowship divine!We feebly struggle, they in glory shine;yet all are one in thee, for all are thine.Alleluia, Alleluia! And when the strife is fierce, the warfare long,steals on the ear the distant triumph song,and hearts are brave again, and arms are strong.Alleluia, Alleluia! From earth’s wide bounds, from ocean’s farthest coast,through gates of pearl streams in the countless host,singing to Father, Son, and Holy Ghost:Alleluia, Alleluia!