Spoiler alert: You’re not going to get a definitive answer to this question. You may be more confused than ever! I know I am. There seem to be dozens of versions of this and similar spirituals. We are singing something close to the one that Carl Sandburg published in his 1927 American Songbag..
Here are just some of the variants of our first verse:
“Mary” is sometimes “Sister Mary” or “Sis Mary”
“Three links of chain” is sometimes “three silver chain[s]”
“Every link bearin’ Jesus’ name” is sometimes “bearin’ freedom’s name” or “each chain bore the Savior’s name”
“Matthew Mark and Luke and John” is sometimes “Gabriel stood and blowed his horn” or “You better let God’s chillun alone.”