Jacob set a pillar, as a monument or memorial of her life and death, and as a testimony of her future resurrection. Unto this day, i.e. unto the time wherein Moses writ this book, and long after. See 1 Samuel 10:2 Jeremiah 31:15.
Related Commentaries of Genesis 35:20
Genesis 35:20
20 And Jacob set a pillar upon her grave: that is the pillar of Rachel's grave unto this day.