Why would Lehi, a descendant of Manasseh, son of Joseph (1 Nephi 5:14; 6:2; 2 Nephi 3:4, 22; Alma 10:3), perform sacrifices when, in Old Testament times, only members of the tribe of Levi were allowed to do so?
Even in the Bible, there are instances of men of non-Levite lineage offering sacrifices. One example that comes to mind is that of Gideon, a judge of Israel, who, like Lehi, was from the Josephite tribe of Manasseh. Commanded of God to build an altar, Gideon made an acceptable burnt offering to the Lord, and was in no way condemned for his action (See Judges 6:24-26). The prophet Samuel was from the Josephite tribe of Ephraim, yet he too offered sacrifices (1 Samuel 1:1; 7:9-10; 10:8; 13:15). The general consensus among Bible scholars is that the idea that only descendants of Aaron could offer sacrifices was a late (post-exilic) concept in ancient Israel. It led to such anomalies as the later chroniclers (who revised the history found in the books of Samuel and Kings) assigning Samuel (pronounced Shemuel in Hebrew) to the tribe of Levi in 1 Chronicles 6:33-38 to justify his having offered sacrifices. Solomon not only offered sacrifices, but it was he, not the high priest, who dedicated the Jerusalem temple (1 Kings 8). It is interesting that the first sacrifice offered for the Israelites after they left Egypt was performed not by a Levite, but by Jethro, the father-in-law of Moses, a non-Israelite (Exodus 18:12).
The Nephites undoubtedly performed sacrifices and temple rites under the Melchizedek priesthood rather than the Aaronic. Indeed, one Israeli scholar (archaeologist Benjamin Mazar, who served as president of the Hebrew University in Jerusalem) has suggested that the Israelite temple in Arad, built while the Jerusalem temple was in operation, had priests of the line of Jethro officiating. From D&C 84:6-7, we learn that Moses received the priesthood from Jethro, and early Jewish and Christian texts indicate that Jethro’s descendants served in the Jerusalem temple, alongside priests of the Aaronic order, in the time of Christ.