The 1st South Carolina Volunteer Infantry (Colored) was one of the first African-American regiments to be raised in the war. Its origins lay in an abandoned experiment by Major General David Hunter to arm escaped slaves in order to defend his exposed position on the Atlantic coast. The experiment failed, mainly because Hunter’s approach was extremly heavy-handed, but it formed to core of what was to become the 1st South Carolina Volunteer Infantry. A company of its soldiers already conducted small raids on November 1862, but the regiment was not mustered in before January 31, 1863. 
On January 1, 1863, a big ceremony was held at Port Royal, South Carolina, to celebrate the coming into effect of the Emancipation Proclamation. At this event, the regiment received its flag, which was handed over to Sgt. Prince Rivers and Cpl. Robert Sutton. The flag bore the words “To the First Regiment of South Carolina Volunteers. The Year of Jubilee Has Come.”
What does this phrase mean?
The expression goes back to a custom mentioned in the Bible. There, the “Year of Jubilee” refers to a season of festival occuring every fifty years, where debts were forgiven, wealth was redistributed and all servants of Hebrew origin obtained their freedom. Educator and writer Maria Richards described it in 1858 as a year of festivities, which was announced by a trumpet proclaiming “liberty to the bondsman, plenty to the impoverished, home to the exile.” 
In the growing abolitionist movement of the antebellum period, this biblical idea took on a meaning that was narrower but at the same time more concise. No longer referring to a general social reform, it referred to the freeing of slaves in the U.S. and the abolition of the institution of slavery. William Goodell, a radical abolitionist, published a newspaper called American Jubilee during the 1850s and abolitionist William Lloyd Garrison often signed his letters with phrases like “Yours to usher in the Jubilee”. 
When the Civil War broke out, many slaves interpreted the events in an almost millennial way, seeing the events as heralding a new age brought forth through an awful conflegration. The notion and concept of Jubilee again provided a way to frame their hopes and make sense of what was happening in religious terms. Black congregations were heard to fervently sing the old methodist hymn “Blow Ye the Trumpet, Blow”, which contained the verse: “The year of jubilee is come! Return, ye ransomed sinners, home.” Union cavalry officer Willard Glazier noted in October 1861 that many slaves come into the federal lines, entertaining “wild notions about a jubilee of liberty, for which they are praying and singing, and look upon us as their deliverers.” Elisha Hunt Rhodes of the 2nd Rhode Island Infantry described visiting “a jubilee meeting” held by African-Americans in May 1862. 
Northern composer and songwriter Henry C. Work, who had connections to the abolitionist movement, took up the term and further developed its meaning in his 1862 song “Kingdom Coming.” Using snippets of African-American speech he had heard, his song tells the story of a Union raid on the South Carolina coast from the perspective of the slaves. Intended as a humorous song, the lyrics exegerate the African-American accent and would probably be considered to be a kind of ‘blackface’ farce today. But the widely popular song also developed the idea of Jubilee in an significant way:
Say, darkies, hab you seen de massa, wid de muffstash on his face, Go long de road some time dis mornin', like he gwine to leab de place? He seen a smoke way up de ribber, whar de Linkum gunboats lay; He took his hat, and lef' berry sudden, and I spec' he's run away! CHORUS: De massa run, ha, ha! De darkey stay, ho, ho! It mus' be now de kingdom coming, an' de year ob Jubilo!
In Work’s song, the day of Jubilee is initiated and enforced by the Union army. It is not an event happening through divine providence or political campaigning, but because the Union war machine with its steam gunboats is fighting and driving away the slave holders. However, it not only gives agency to the Union soldiers, but also to the slaves themselves, which are depicted as taking over the plantation and locking the overseer into the cellar.
African-Americans of course had not waited for the Union army, but had employed their own agency to usher in the year of Jubilee. They knew that escaping from their owners and coming into Union lines, as Glazier wittnessed, already meant taking their fate into their own hands. For many African-American men, joining the Union army was another step in this process.
It is altogether fitting, then, that the regimental flag of the 1st S. C., which was sewn by members of the congregation from the antislavery Church of the Pilgrims in New York, bore the inscription: “The Year of Jubilee Has Come.” African-American soldiers fighting under it were always reminded that they themselves, former slaves, finally had the authority as well as the military power to contribute to the fight for freedom from their chains.
 For the history of the regiment see Saucer, John: An We Ob Jubilee: The First South Carolina Volunteers. Arcadia Publishing 2019 and Ash, Stephen V.: Firebrand of Liberty. The Story of Two Black Regiments that Changed the Course of the Civil War. New York, London: W. W. Norton & Co. 2008.
 Richards, Maria Tolman: The Year of Jubilee: Or, Familiar Phases of Hebrew Life. New York: Sheldon, Blakeman & Co. 1858, p. 117.
 Coffey, John: Exodus and Liberation: Deliverance Politics from John Calvin to Martin Luther King. Oxford: Oxford University Press, p. 125.
 Glazier, Willard W.: Three Years in the Federal Cavalry. New York: Ferguson & Co. 1873, p. 40; Rhodes, Robert Hunt (ed.): All for the Union. The Civil War Diary and Letters of Elisha Hunt Rhodes. New York: Random House 1992, p. 57.