Definitions: Cleanliness is the careful avoidance of dirt. Tidiness is neatness; orderliness.

1. Cleanliness and tidiness is an important part of our testimony to others.

2 Corinthians 3:2 [Your sample speaks louder than words] Ye are our epistle written in our hearts, known and read of all men.
2 Corinthians 6:3 Giving no offence in any thing, that the ministry be not blamed.
1 Thessalonians 5:22 Abstain from all appearance of evil.
2 Thessalonians 3:7-11 For yourselves know how ye ought to follow us: for we behaved not ourselves disorderly among you. … 9 Not because we have not power, but to make ourselves an ensample unto you to follow us. … 11a For we hear that there are some which walk among you disorderly, working not at all.
1 Timothy 4:12 Let no man despise thy youth; but be thou an example of the believers, in word, in conversation [behavior, manner of life], in charity [love], in spirit, in faith, in purity.
1 Timothy 5:10 [Paul describes the testimony of a faithful widow, as one who washed the feet of brethren who visited, which was an important part of keeping a clean house, as well as a loving courtesy to visitors:] Well reported of for good works; if she have brought up children, if she have lodged strangers, if she have washed the saints’ feet, if she have relieved the afflicted, if she have diligently followed every good work.
Titus 2:7a In all things shewing thyself a pattern of good works.

2. Cleanliness is not “next to godliness,” it’s part of it!

Psalm 51:7 [Spiritual washing is a parallel of physical washing. Dirt is a parallel of sin] Purge me with hyssop [a sweet smelling plant used for cleansing and perfumery], and I shall be clean: wash me, and I shall be whiter than snow…. 10 Create in me a clean heart, O God; and renew a right spirit within me.
Psalm 119:9 Wherewithal shall a young man cleanse his way? By taking heed thereto according to Thy Word. [See also James 1:21]
Isaiah 1:16 Wash you, make you clean; put away the evil of your doings from before Mine eyes; cease to do evil.
Matthew 23:25-28 [The Pharisees were physically immaculate, but spiritually filthy] 25 Woe unto you, scribes and Pharisees, hypocrites! For ye make clean the outside of the cup and of the platter, but within they are full of extortion and excess. 26 Thou blind Pharisee, cleanse first that which is within the cup and platter, that the outside of them may be clean  also. 27 Woe unto you, scribes and Pharisees, hypocrites! For ye are like unto whited sepulchres, which indeed appear beautiful outward, but are within full of dead men’s bones, and of all uncleanness. 28 Even so ye  also outwardly appear righteous unto men, but within ye are full of hypocrisy and iniquity.
John 15:3 Now ye are clean through the Word which I have spoken unto you. [See also 17:17]
2 Corinthians 7:1 Having therefore these promises, dearly beloved, let us cleanse ourselves from all filthiness of the flesh and spirit, perfecting holiness in the fear of God.
Galatians 5:19 Now the works of the flesh are manifest, which are these; adultery, fornication, uncleanness, lasciviousness.
1 Thessalonians 4:7 For God hath not called us unto uncleanness, but unto holiness. [See also Romans 6:19]
2 Timothy 2:21 If a man therefore purge himself from these, he shall be a vessel unto honour, sanctified, and meet for the Master’s use, and prepared unto every good work.
James 1:21 [Cleanse yourself inside and outside] Wherefore lay apart all filthiness and superfluity [the abundance] of naughtiness, and receive with meekness the engrafted Word, which is able to save your souls.
Hebrews 10:22 Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water. [See also Ezekiel 36:25; James 4:8]
1 John 1:7,9 But if we walk in the light, as He is in the light, we have fellowship one with another, and the blood of Jesus Christ His Son cleanseth us from all sin. … 9 If we confess our sins, He is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.

3. God created the world to be orderly and neat.

Genesis 1:14,24 [God established regularity and uniformity at Creation:] And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years. … 24 And God said, Let the earth bring forth the living creature after his kind, cattle, and creeping thing, and beast of the earth after his kind: and it was so.
Genesis 8:22 [God reaffirmed the order of the natural world after the Flood:] While the earth remaineth, seedtime and harvest, and cold and heat, and summer and winter, and day and night shall not cease.
Ecclesiastes 1:4-7 [Divine harmony and the orderliness is seen in the course of nature from generation to generation] One generation passeth away, and another generation cometh: but the earth abideth for ever. 5 The sun  also ariseth, and the sun goeth down, and hasteth to his place where he arose. 6 The wind goeth toward the south, and turneth about unto the north; it whirleth about continually, and the wind returneth again according to his circuits. 7 All the rivers run into the sea; yet the sea is not full; unto the place from whence the rivers come, thither they return again.
1 Corinthians 14:33a For God is not the author of confusion.

4. From the beginning God intended for mankind to be caretakers of His creation.

Genesis 1:26-28 [God entrusted man with dominion over the earth, — quite a responsibility:] And God said, Let Us make man in Our image, after Our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth. 27 So God created man in His Own image, in the image of God created He him; male and female created He them. 28 And God blessed them, and God said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth.
Genesis 2:15 [One of Adam’s first responsibilities was to keep the garden in good condition:] And the Lord God took the man, and put him into the Garden of Eden to dress it and to keep it.
1 Corinthians 14:40 Let all things be done decently and in order.
1 Corinthians 3:16,17 [Because our bodies are God’s temple, we need to take good care of them, or we’ll suffer for it] Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you? 17 If any man defile the temple of God, him shall God destroy; for the temple of God is holy, which temple ye are. [See also 1 Corinthians 6:19,20]
1 Corinthians 4:2 Moreover it is required in stewards, that a man be found faithful.
Colossians 2:5 [Paul, as an overseer of the Church,  also praised those who kept their work orderly] For though I be absent in the flesh, yet am I with you in the spirit, joying and beholding your order, and the steadfastness of your faith in Christ. [See also Titus 1:5]

5. Whole chapters of the Old Testament, particularly in Leviticus and Deuteronomy, are devoted to detailing specific rules regarding cleanliness and sanitation. Although we are no longer under the Mosaic Law, many of the general principles still apply today and are vital to good health.

Exodus 19:10 And the Lord said unto Moses, Go unto the people, and sanctify them to day and to morrow, and let them wash their cloths
Exodus 40:30-32 And he set the laver [basin] between the tent of the congregation and the altar, and put water there, to wash withal. 31 And Moses and Aaron and his sons washed their hands and their feet thereat: 32 When they went into the tent of the congregation, and when they came near unto the altar, they washed; as the Lord commanded Moses.
Leviticus 10:10 And that ye may put difference between holy and unholy, and between unclean and clean.
Leviticus 11:44a For I am the Lord your God: ye shall therefore sanctify [cleanse, purify] yourselves, and ye shall be holy; for I am holy. [See also 45-47]
Exodus 15:26a And said, If thou wilt diligently hearken to the voice of the Lord thy God, and wilt do that which is right in His sight, and wilt give ear to His commandments, and keep all His statutes, I will put none of these diseases upon thee.
Ezekiel 44:23 [The Lord wanted to teach His people a good standard of cleanliness] And they shall teach My people the difference between the holy and profane, and cause them to discern between the unclean and the clean.