Is it permissible to pray in work clothes?

One of the conditions of prayer is purification from impurity (najasa). There should be no impurities that prevent prayer, such as blood, urine, wine, or feces, on the clothes, body, or the place where the person will pray. (Marghinani, al-Hidaya, 1/36)

Stains such as whitewash, paint, mineral oils, rust, and similar dirt found on work clothes depending on the type of work are not considered impurities and therefore do not affect the validity of the prayer. However, it is recommended in the Qur’an for a person going to the mosque for prayer to wear clean clothes. (al-A'raf, 7/31)

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu