20 And ye shall offer for a sacrifice unto me a broken heart and a contrite spirit….

When it says the sons of Levi will offer a sacrifice in righteousness it never mentions blood. Was what Joseph Fielding Smith said direct revelation and answer to prayer? Could it have been an opinion or guess as to what it could mean?

Amulek explained the fulfillment of the law this way:

“Therefore, it is expedient that there should be a great and last sacrifice, and then shall there be … a stop to the shedding of blood; then shall the law of Moses be fulfilled. …

“And behold, this is the whole meaning of the law, every whit pointing to that great and last sacrifice; and that great and last sacrifice will be the Son of God, yea, infinite and eternal” (Alma 34:13–14).
While the law of Moses was fulfilled, the principles of the law of sacrifice continue to be part of the doctrine of the Church. The primary purpose of the law of sacrifice still is to test us and assist us in coming unto Christ. After the Savior’s ultimate sacrifice, two adjustments were made in the practice of this law. First, the ordinance of the sacrament replaced the ordinance of sacrifice; and second, this change moved the focus of the sacrifice from a person’s animal to the person himself. In a sense, the sacrifice changed from the offering to the offerer.

Blood sacrifice was always symbolic. I believe… this may already be fulfilled. As we contemplate the replacing of animal sacrifice with the sacrament, we cannot help but notice a strong relationship between the two. Both sacrifice and sacrament:

• Are affected by a person’s attitude and worthiness (see Amos 5:6–7, 9–10, 21–22; 3 Ne. 18:27–29; Moro. 7:6–7).
• Are designed to be performed by priests officiating in the Aaronic Priesthood (see D&C 13:1; D&C 20:46).
• Focus on Christ (see Luke 22:19–20; Alma 34:13–14).
• Use emblems that represent Christ’s flesh and blood (see Luke 22:19–20; Moses 5:6–7).
• Provide a means whereby one can make and renew covenants with God (see Lev. 22:21; D&C 20:77, 79).
• Are performed regularly on the Sabbath as well as on other special occasions (see Lev. 23:15; D&C 59:9–13).
• Are associated with meals that symbolically represent the Atonement (see Lev. 7:16–18; Matt. 26:26).
• Are the only saving ordinances in which members participate for themselves more than once.
• Provide an important step in the process of repentance (see Lev. 19:22; 3 Ne. 18:11; Moses 5:7–8).
I got most of this from a talk by M Russel Ballard,”The Law of the Sacrifice” https://www.lds.org/liahona/2002/03/the-law-of-sacrifice?lang=eng