Mary was the holiest creature God ever created. This can be affirmed in three ways:
Her role as the true Ark of the Covenant
Her closeness to God; and
Her hierarchy in the order of grace.
Ark of the Covenant
In the first way, we know that Mary is the true Ark of the Covenant. The original Ark of the Covenant was considered holy as it resided within the Holy of Holies (Hebrews 9:1-5) where God chose to interact with the priest. If the Ark was considered holy, how much more the true Ark of the Covenant, for Christ, the Son of God, chose to reside in her womb for nine months and chose to reside in her home for close to 30 years.
Closeness to God
In the second way, we see that before Christ, God spoke to the people through mediators who were holy and held in great esteem. The closer they were to God, the greater their holiness because of this closeness.
As such Abraham, Isaac and Jacob who were the fathers of the chosen people are personally associated with God (Acts 3:13), Moses and Elijah who talk on behalf of God with signs and wonders personally attend to Christ (Matthew 17:1-3) and St. John the Baptist who is Christ’s cousin and the one to clear the path for His coming is considered by Christ Himself the greatest born among woman (Matthew 11:11).
But if these men are considered great and holy, how much more is Mary who personally gave birth to Christ and raised Him in wisdom (Luke 2:52)?
If proximity to God is holiness, and if nothing is humanly closer than the relationship between a mother and child (1 Thessalonians 2:7), then Mary is the holiest creature God ever created because she is the Mother of God.
Hierarchy in the Order of Grace
In the natural order we see that some creatures are stronger than others, some are faster than others, some are smarter than others, some are more adaptable than others. In the supernatural order (also known as “The order of grace”)1, some are more courageous than others, some are more tempered than others, some are more just than others, some are more prudent than others.
Who then was God’s most humble creature? Mary. Why? Because, just as the King of Kings, Jesus Christ, was declared humble because He became man, lived a life of poverty and was obedient up to His death (Philippians 2:5-11), the Queen Mother of the King of Kings, Mary, is also humble because she lived in the same manner, having lived a life of poverty and was obedient up to her death. If Christ is the pinnacle of humility, the Mary follows immediately after.
If God gives more grace to those who are more humble (James 4:6), then Mary, being the most humble creature in the order of grace, is also filled with the most grace making her that much more holy.
And if God exalts the humble (James 4:10), then Mary, by virtue of her humility is also the most exalted creature by God. To exalt means to elevate the rank.1 Mary then, in rank, is the holiest creature God ever created.