12:23 church of the firstborn. The “church of the firstborn” will have all Christians of all times as its members. It will have its first full “assembly” in the future age, but presumably does meet on occasion even now, with the “spirits of [justified] men made perfect” coming together for fellowship and testimony.

12:24 than that of Abel. Compare Genesis 4:10 and Hebrews 11:4, on the “voice” of Abel’s blood.