Psalm 99 is a wonderful psalm of worship. Spurgeon called it the “holy, holy, holy” psalm, for it is punctuated by three declarations of God’s holiness (vv3,5,9). These declarations divide the psalm into three stanzas, or strophes, of unequal length, each of which presents us with a different characteristic of God, a different motivation for our worship and appreciation. In verses 1-3, the emphasis is on divine rule: “The Lord reigneth” (v1). Verses 4 and 5 focus on divine righteousness: “Thou executest judgment and righteousness in Jacob” (v4). The final – and longest – section of the psalm is a meditation on divine revelation: “He spake unto them in the cloudy pillar” (v7). In this section, however, the psalmist is not just occupied with the truth of revelation, awe-inspiring though it is. He marvels not just at divine revelation but at divine response and relationship; not just that God speaks but that He answers (vv6,8). That truth, remarkable at any time and in any context, gains lustre from its setting in a psalm that so emphasises the holiness of God. Holiness means separation. God is apart from, distinct from His creation. But he is not remote. In grace He responds to their prayers and answers their requests, and He has done so, not just sporadically, but consistently, not just in the nation’s good days, but in its bad days too.
As he reviews the record of God’s communion with the nation, the psalmist recalls those to whom He spoke in a remarkable way: “Moses and Aaron among his priests, and Samuel among them that call upon his name; they called upon the Lord, and he answered them” (v6). The names that are included here are no surprise, but what is unexpected is the identification of Moses as a priest. We are well accustomed to thinking of Aaron as a priest, so much so that it is difficult for us to think about priestly service without also thinking about Aaron. But the idea of Moses as a priest is altogether less familiar, or at least less familiar to us – a range of Second Temple Jewish writers had no difficulty in describing Moses as a priest.
And perhaps it ought not to be so surprising to us either. After all, Moses, at various points during his life, carried out many of the activities that we have seen to be associated with priestly service. While his was not a priesthood in the formal and official sense that Aaron’s was, he played a vital role in introducing and supporting the Aaronic priesthood and in mediating the covenant.
Moses’ introductory ministry is evident at a number of the most significant occasions in the establishment of the Aaronic order of priesthood. So, for example, we find him offering sacrifices at the giving of the Law in Exodus 24, and at the consecration of the High Priest in Exodus 29. When the Tabernacle was erected for the first time, it was Moses who was responsible for the placement of the furniture within the Tabernacle, essentially commissioning it as a place of priestly service (Exo 40). He was central, too, to the inauguration of both the priests and the Levites (Exo 29; Lev 8); it was his responsibility to carry out the rites of consecration. In these ways, Moses’ priesthood was foundational to and preparatory for that of Aaron and his sons.
Moses also supported Aaron in the discharge of his priestly duties. It is a worthwhile study to trace the references throughout Scripture to “Moses and Aaron” and to see the ways in which these two brothers supported and complemented each other in the discharge of responsibilities that were, to put it mildly, considerable. Oftentimes, there was nothing specifically priestly about their collaboration, but at times we can see them united in priestly activity. Numbers 3:38 gives us a particularly clear instance of this: “But those that encamp before the tabernacle toward the east, even before the tabernacle of the congregation eastward, shall be Moses, and Aaron and his sons, keeping the charge of the sanctuary for the charge of the children of Israel; and the stranger that cometh nigh shall be put to death.” At times, too, we see Moses in association with Eleazar (Num 26:1-3; 31:51-54) and, in Deuteronomy 27:9, “Moses and the priests the Levites spake unto all Israel, saying, Take heed, and hearken, O Israel; this day thou art become the people of the Lord thy God.”
This is just one instance where we see Moses mediating the Word of God to the people of God. In a very particular and unique way, he fulfilled the words of Malachi 2:7: “For the priest’s lips should keep knowledge, and they should seek the law at his mouth.” John 1:17 tells us that “the law was given through Moses.” This verse, along with Galatians 3:19-20, makes it clear that Moses functioned as a mediator in the giving of the Law. At Sinai, he went alone into the presence of God. The clear priestly significance of this act may be underscored by points of resemblance between Sinai and the tabernacle: “Like the tabernacle, Mount Sinai has a dark covering over it, but contains [Jehovah’s] glory within. There are different degrees of access permitted. The people have to maintain a perimeter around the mountain and are not permitted to touch it (Exo 19:12-13). The elders of Israel eat directly beneath the firmament (24:9-11), the veil of which is opened so that they behold [Jehovah]. However, Moses goes into the very midst of the cloud where [Jehovah] is (24:12-18). These different regions correspond to the different parts of the tabernacle. Israel, camped before the mountain, is in the court of the tabernacle, where the altar and laver are found. The elders went into the Holy Place, where they ate at the equivalent of the table of showbread, before the veil of the Holy of Holies. Moses, however, passed through that veil and went into the very presence of [Jehovah] in His throne room, where the tablets of the covenant were given.”
Moses’ mediatorship did not just consist of coming out from God’s presence to bring God’s revelation to His people. On a number of occasions, he represented the nation before God, and his intercession with God on behalf of the nation played a vital role in its preservation and blessing. Nowhere, perhaps, is this clearer than in Exodus 32 where, in the aftermath of the golden calf, Moses pleads with God on behalf of the people: “And it came to pass on the morrow, that Moses said unto the people, Ye have sinned a great sin: and now I will go up unto the Lord; peradventure I shall make an atonement for your sin. And Moses returned unto the Lord, and said, Oh, this people have sinned a great sin, and have made them gods of gold. Yet now, if thou wilt forgive their sin–; and if not, blot me, I pray thee, out of thy book which thou hast written” (vv30-32). Moses’ entrance into the presence of God, his intercession with God, and the language he uses (“make an atonement”) combine to make it clear that this is a man engaged in priestly service.
This theme continues in the following chapter. Again, Moses intercedes with God, not just to deliver the nation but to promise His presence with them. As he pleads for the nation, Moses makes two requests: “Shew me now thy way,” he asks, “I beseech thee, show me thy glory” (33:13,18). In response to the first request, God promises His presence with the nation. Moses’ second request is not directly fulfilled – he doesn’t get to see what God looks like. But what he does get is a revelation of what God is like: “I will make all my goodness pass before thee, and I will proclaim the name of the Lord before thee; and will be gracious to whom I will be gracious, and will shew mercy on whom I will shew mercy (v19).
“They called upon the Lord, and he answered them” (Psa 99:6). Whether or not he was thinking specifically of Exodus 33 (and I suspect he may well have been), the psalmist understood that the God of response and relationship was worthy of worship, from Moses and Aaron – and me and you – among his priests, and Samuel – and me and you – among them that call upon His name.
 All Scripture quotations in this article are from the KJV.
 Not everyone is agreed that the Hebrew grammar of the psalm allows (or requires) Moses to be viewed as a priest. See the discussion in M.E. Tate, Psalms 51-100, Word Biblical Commentary (Grand Rapids, MI: Zondervan, 1990), 527, and John Goldingay, Psalms 90-150, Baker Commentary on the Old Testament Wisdom and Psalms (Grand Rapids, MI: Baker Academic, 2003), 130.
 See Andrew S. Malone, God’s Mediators: A Biblical Theology of Priesthood, New Studies in Biblical Theology (Downers Grove, IL: Inter-Varsity Press, 2017), 64-65, and the list of sources in Jacob Milgrom, Leviticus 1-16, Anchor Yale Bible Commentary (New Haven, CT: Yale U.P., 1991), 555-558.
 Alasdair Roberts, “A Portable Mountain and Competing Calves,” https://alastairadversaria.com/2013/03/23/a-portable-mountain-and-competing-calves-40-days-of-exoduses-19/, accessed 30 September 2021.