We are trav’ling in the footsteps
Of those who’ve gone before,
And we’ll all be reunited,
On a new and sunlit shore,
Oh, when the saints go marching in
Oh, when the saints go marching in
I want to be in that number
When the saints go marching in
And when the sun refuse to shine
And when the sun refuse to shine
I want to be in that number
When the sun refuse to shine
And when the moon turns red with blood
And when the moon turns red with blood
I want to be in that number
When the moon turns red with blood
Oh, when the trumpet sounds its call
Oh, when the trumpet sounds its call
I want to be in that number
When the trumpet sounds its call
Some say this world of trouble,
Is the only one we need,
But I’m waiting for that morning,
When the new world is revealed.
Oh When the new world is revealed
Oh When the new world is revealed
I want to be in that number
When the new world is revealed
Oh, when the saints go marching in
Oh, when the saints go marching in
I want to be in that number
When the saints go marching in

The song is apocalyptic, taking much of its imagery from the Book of Revelation, but excluding its more horrific depictions of the Last Judgment. The verses about the Sun and Moon refer to Solar and Lunar eclipses; the trumpet (of the Archangel Gabriel) is the way in which the Last Judgment is announced. The phrase “I want to be in that number” refers to the specific number of “144,000 who had been redeemed from the earth”, given as prophecy in Revelations. The Bible speaks of these people as being “sealed” as “servants of God”, without specifically calling them saints. As the hymn expresses the wish to go to Heaven, picturing the saints going in (through the Pearly Gates), it is entirely appropriate for funerals.

From Wikipedia