Is it permissible to pray in clothes that have dirt on them resulting from their contact with the body, such as the collar of a shirt or trousers?

Prayer is valid in soiled clothing if it is pure and no impurity has fallen upon it. There is no harm in praying in clothes that have sweat or non-impure dirt, or old clothes that cover the 'awrah (private parts). However, it is better for the worshipper to choose clean clothes, based on the Almighty's saying: "O Children of Adam, take your adornment [i.e., clean clothes] at every masjid," and the Prophet (peace be upon him) said: "When one of you prays, let him wear his two garments, for Allah is most deserving of adornment for Him."