The Bible says much more about consecrating than about sanctifying or making holy. As a general distinction: God sanctifies, man consecrates. In the matter of holiness, there is God’s part and man’s part. Man cannot make anything holy, but man can act in obedience to God’s commands and work in partnership with God so that He will make something holy. God does His part when man does his part.
For example, when Moses and Aaron did what God told them to do to consecrate the tabernacle, God responded by sanctifying it with His glory.
The English word sanctify (from holy plus to make) is defined as: 1. To make holy; to set apart to a sacred office or to religious use. 2. to make free from sin; to purify.
The English word consecrate (from with or together plus sacred) is defined as: To make or declare sacred or holy; to set apart or devote to the service or worship of God.
A. God’s people.
Before the Lord gave the law to Moses on tablets of stone, He spoke the law verbally from Mount Sinai for all the people to hear. In preparation for this event, God commanded the people and the priests to consecrate themselves by washing their clothes and then abstaining from sexual relations until the third day. They were also commanded to stay off the mountain on pain of death.
God’s part. Following this, God spoke to the people from heaven and gave them the Ten Commandments. These commands describe what followers of God should be like—how God wants His people to be different from the world.
B. The priests.
Aaron and his sons, and all who held priestly office, needed to be consecrated or set apart for the service of God before they served God in His house and helped others to worship God in holiness.
The priests went through an ordination process similar to, yet far more detailed, than did the people of God. The people washed their clothes. The priests washed themselves and wore special clothing—“holy garments” designed by highly skilled men inspired by wisdom from God. God told Moses, “You shall put them on Aaron your brother, and on his sons with him, and shall anoint them and ordain them and consecrate them, that they may serve me as priests.”
God gave Moses step by step instructions as to how to consecrate the priests for the Lord’s service. “Now this is what you shall do to them to consecrate them, that they may serve me as priests.” First Moses was to select the animals to be sacrificed, then bring Aaron and his sons to the entrance of the tent of meeting and wash them with water, then dress them in their special garments.
Aaron and his sons were to identify with the animals being sacrificed by laying their hands on the head of each animal before it was killed. When anointing oil and some of the blood of the sacrifice were sprinkled on the priests and on their garments, the priests and their garments were made holy. The priests went through the ceremony; the Lord made them holy.
Once the priests were made holy, they were able safely to eat part of the sacrifice. This food—the bread and the breast and thigh of the ram—was consecrated, or set apart, by first being waved and lifted up before the Lord.
The ordination process took seven days. “Do for Aaron and his sons everything I have commanded you, taking seven days to ordain them.” During this time the priests were to stay at the entrance to the Tent of Meeting and make daily sacrifices.
After the ordination, the priests were to wash whenever they came to the tabernacle. “When they go into the tent of meeting, or when they come near the altar to minister, to burn a food offering to the Lord, they shall wash with water, so that they may not die. They shall wash their hands and their feet, so that they may not die.”
God’s part. Once the priests had done their part, God’s first reaction was to allow them to live. Then God consecrated them. Then He dwelt among them! The Lord told Moses, “Aaron also and his sons I will consecrate to serve me as priests. I will dwell among the people of Israel and will be their God. And they shall know that I am the Lord their God, who brought them out of the land of Egypt that I might dwell among them. I am the Lord their God.”
C. The altar, the tabernacle and its furnishings
The altar was consecrated during the seven-day ordination of the priests by the sacrifices which were made on it. Each day the blood of the sacrifice was sprinkled against all sides of the altar, and the altar was anointed with sacred anointing oil.
The tabernacle was consecrated by the sacrifices made on the altar in front of it. The tabernacle and all its contents were also anointed with sacred oil.
Then we see man’s part and God’s part blend together. “You shall consecrate them, that they may be most holy. Whatever touches them will become holy.” “The altar shall be most holy. Whatever touches the altar shall become holy.”
God promised, “I will consecrate the tent of meeting and the altar.” He also promised, “There I will meet with the people of Israel, and it shall be sanctified by my glory.” 
All of the instructions for the priests and the altar, the tabernacle, and its furnishings were carried out to the letter in Leviticus 8 and 9. Then Moses and Aaron were finally able to enter the Tent of Meeting briefly. When they came out, they blessed the people—and then the Lord sanctified the Tent of Meeting by His glory.
The pillar of cloud which directed the movements of the Israelites “covered the tent of meeting, and the glory of the Lord filled the tabernacle. And Moses was not able to enter the tent of meeting because the cloud settled on it, and the glory of the Lord filled the tabernacle.” The account in Leviticus continues: “And the glory of the Lord appeared to all the people. And fire came out from before the Lord and consumed the burnt offering and the pieces of fat on the altar, and when all the people saw it, they shouted and fell on their faces.”
What happened next is mind-boggling.
“Now Nadab and Abihu, the sons of Aaron, each took his censer and put fire in it and laid incense on it and offered unauthorized fire before the Lord, which he had not commanded them. And fire came out from before the Lord and consumed them, and they died before the Lord.” As Aaron stared in stunned silence at his dead sons, Moses turned to him and said, “This is what the Lord has said: ‘Among those who are near me I will be sanctified, and before all the people I will be glorified.’” And Aaron held his peace. 
Nadab and Abihu had just gone through seven days of ordination and consecration. They should have been meditating on the meaning of all the rituals. Every detail pointed to God’s holiness and man’s sinfulness. The bloody sacrifices showed how God views sin—the wages of sin is death. The sacrificial animals died in place of the sinful people and even the sinful priests.
Nadab and Abihu had grasped none of this. They acted on the spur of the moment, improvising when they should have been adhering strictly to script. And they died for their insolence.
F. Lessons learned.
What do we learn from all this?
We begin as a people who dare not come into God’s presence on pain of death.
Wash. God’s commands us to wash ourselves and wash our clothes. This is a picture of repentance.
Put on holy garments. Recognize that good works done in our own strength are worthless. “All our righteousnesses are as filthy rags.” We need to put on Christ’s righteousness.
Lay your hand on the head of the sacrifice. Identify with the Lamb of God. Recognize that He died in your place.
Only after all this can we enter the Tabernacle—come into the presence of God. After our initial repentance we need only wash our hands and our feet when we sin again. Confess your sins, and God will forgive you. You don’t need to be saved all over again.
Consecrate yourself to God, and He will sanctify you – make you holy.
 For this study I have used the English Standard Version. Why ESV? The English Standard Version, published in 2001, is “an ‘essentially literal’ translation that seeks to capture the precise wording of the original text” (Decision, Sept. 2017, p. 25). The ESV uses the word “sanctify” 15 times in the Old Testament compared to 78 times for “consecrate.”
 Ex. 19:10-15, 22
 Ex. 28:3-4, 41; 29:4-9
 Ex. 29:1. Instructions continue throughout the chapter.
 Ex. 29:21
 Ex. 29:35, NIV
 Ex. 30:20-21
 Ex. 29:44-46
 Ex. 30:25-28
 Ex. 30:29
 Ex. 29:37
 Ex. 29:43, 44
 Ex. 40:34-35
 Lev. 9:23-24
 Lev. 10:1-3
 Isa. 64:6
 1 John 1:9