Praise be to Allah.
Being overly concerned with ones appearance is the kind of extreme action that is condemned, because Islam is the religion of moderation that favours the middle path between extremes of any kind. Allaah said (interpretation of the meaning):
O Children of Adam! Take your adornment (by wearing your clean clothes) while praying [and going round (the Tawaaf of ) the Kabah] and eat and drink but waste not by extravagance, certainly He (Allaah) likes not Al-Musrifoon (those who waste by extravagance). [al-Araaf 7:31]
So Allaah has commanded us to take our adornment when coming to the mosque to pray, and He has permitted us to eat and drink, then He warned us against being extravagant and going to extremes, and has told us that He does not love those who waste by extravagance.
And Allaah said (interpretation of the meaning):
But spend not wastefully (your wealth) in the manner of a spendthrift. Verily, the spendthrifts are brothers of the Shayaateen (devils), and the Shaytaan (Devil-Satan) is ever ungrateful to his Lord [al-Israa 17:26-27]
The spendthrift is the brother of the Shaytaan and shares the same attitude, because he wastes money and spends it on things that are of no benefit. The measure of whether a thing is of no benefit is as the scholars said: if it is of no benefit in either religious or worldly terms.
The Muslims attitude should be as Allaah described it (interpretation of the meaning):
And those who, when they spend, are neither extravagant nor niggardly, but hold a medium (way) between those (extremes) [al-Furqaan 25:67]. They tread a middle path between miserliness and overspending. Ibn Abbaas (may Allaah be pleased with him) said: Eat and drink and dress as you like, so long as you do not have two qualities: extravagance and showing off.
Many people are keen to make sure that their outward appearance is the best and cleanest and most proper, then they do not purify their hearts and souls of the diseases against which Allaah has warned us, such as hypocrisy, lying, envy, arrogance, showing off, pride, self-admiration, wrongdoing, ignorance and hatred towards the believers, or evil forbidden desires, etc. Allaah has told us that the garment of faith and taqwa (piety) is better than the outward garments. Allaah says (interpretation of the meaning):
O Children of Adam! We have bestowed raiment upon you to cover yourselves (screen your private parts) and as an adornment; and the raiment of righteousness, that is better. Such are among the Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.) of Allaah, that they may remember (i.e. leave falsehood and follow truth). [al-Araaf 7:26]
The Prophet of Guidance (peace and blessings of Allaah be upon him) told us about the signs of a persons success:
Allaah does not look at the outward appearance or wealth of any one of you, but He looks at your hearts and deeds.
(Narrated by Muslim from the hadeeth of Abu Hurayrah). The heart is the seat of taqwa and a man's essential qualities and the treasures of knowledge, and deeds are the balance in which people will be weighed before Allaah, as Allaah says (interpretation of the meaning):
Verily, the most honourable of you with Allaah is that (believer) who has At-Taqwaa [al-Hujuraat 49:13]
So it is strange indeed that a person would pay attention to how he appears to others, and wash and adorn himself lest there appears to be anything wrong with him, then he does not pay any attention to his heart which is what the Creator looks at, and he does not purify and adorn his heart.
We ask Allaah to reform our hearts and purify our tongues and cause all our faculties to obey Him.