In Surah Muddathir Allah SWT tells the noble Prophet Muhammad peace be upon him to purify your garments. The meaning of this is not just to wear clean clothes, it means also that a person has to lawfully earn from halal permissible means the clothing that he purchases and wears as through lawful honest earnings a person is in obedience to Allah SWT and follows that which is of goodness and upright moral and beautiful modest attire. Also using water to purify and clean yourself from all impurities of the body and using water to clean your clothes as they get dirty throughout daily living. For water is never impure however it can be contaminated and from clean water a person can purify themselves and their clothing and environment meaning there home and wherever they about in the world trying to keep it as clean as possible.
So do not wear clothes of disobedience meaning do not earn unlawful means to purchase your garments and purifying your garments means purifying your heart, body and intention making them as clear and clean as possible and beautify your character removing all those harmful elements that ruin a person such as pride, envy, greed, lust, arrogance, ignorance and many other traits that are best removed by standing in prayer particularly at night time which is better for recitation and reflection as there are less distractions of worldly duties and through prayer purify your heart, beautify your character, increase your beneficial knowledge and beneficial action based on that knowledge as prayer contains a wealth of abundance in terms of wisdom, knowledge, power, might, strength, peace, healing, richness, contentment, self-sufficiency and best of all remembrance and connection directly to Allah SWT.
So for prayer you need to purify first your body with wudu ablution using water and wear purified garments, your heart is purified in this process be modest and you will attain more than everything that the entire world contains and Allah SWT will place abundance of wealth in your heart and between your eyes. The greatest part of purifying your garments is that you will attain and develop a sound heart. This is the reason why the noble Prophet Muhammad peace be upon him loved and prayed often as it was the time when he peace be upon him was closest and at peace with Allah SWT.
The garments a person wears is also different according to each situation or place or person that a person meets, for example your behavior is your garments in the sense that when you go to the masjid to pray you put on your modest and proper clothing particularly that which is clean and loved by yourself and what is appropriate to wear before Allah SWT. Other times a person may attend a wedding and put on an expensive suit or when performing exercise or martial arts wears loose relaxed clothing and in each of the above three mentioned places, the masjid, the wedding or the dojo a person has to maintain behavior according to their understanding of what is proper and correct particularly when they have to be respectful to each other and towards Allah SWT or to the guests at the wedding or to your teacher, the sensei and to fellow students of martial arts in the dojo. So this respectful genuine good behavior is what honest living and purified garments brings into the hearts and lives of the people.