"If God only cares what's on the inside..."
Who ever said that God ONLY cared about the inside?
I was pointed back to the children of Israel anciently, and was shown that God had given specific directions in regard to the material and style of dress to be worn by those who ministered before Him. The God of heaven, whose arm moves the world, who sustains us and gives us life and health, has given us evidence that He may be honored or dishonored by the apparel of those who officiate before Him. He gave special directions to Moses in regard to everything connected with His service. He gave instruction even in regard to the arrangement of their houses and specified the dress which those should wear who were to minister in His service. They were to maintain order in everything and especially to preserve cleanliness.
Read the directions that were given to Moses to be made known to the children of Israel as God was about to come down upon the mount to speak in their hearing His holy law. What did He command Moses to have the people do? To be ready against the third day; for on the third day, said He, the Lord will come down upon the mount in the sight of all the people. They were to set bounds about the mount. "And the Lord said unto Moses, Go unto the people, and sanctify them today and tomorrow, and let them wash their clothes." That great and mighty God who created the beautiful Eden and everything lovely in it is a God of order, and He wants order and cleanliness with His people. That mighty God directed Moses to tell the people to wash their clothes lest there should be impurity in their clothing and about their persons as they came up before the Lord. And Moses went down from the mount unto the people, and they washed their clothes, according to the command of God.
And to show how careful they were to be in regard to cleanliness, Moses was to put a laver between the tent of the congregation and the altar, "and put water there, to wash withal." And Moses and Aaron, and Aaron's sons that ministered before the Lord, were to wash their hands and their feet thereat when they went into the tent of the congregation, and when they went in before the Lord.
This was the commandment of the great and mighty God. There was to be nothing slack and untidy about those who appeared before Him when they came into His holy presence. And why was this? What was the object of all this carefulness? Was it merely to recommend the people to God? Was it merely to gain His approbation? The reason that was given me was this, that a right impression might be made upon the people. If those who ministered in sacred office should fail to manifest care, and reverence for God, in their apparel and their deportment, the people would lose their awe and their reverence for God and His sacred service. If the priests showed great reverence for God by being very careful and very particular as they came into His presence, it gave the people an exalted idea of God and His requirements. It showed them that God was holy, that His work was sacred, and that everything in connection with His work must be holy; that it must be free from everything like impurity and uncleanness; and that all defilement must be put away from those who approach nigh to God.