Is praying in underwear invalid, valid, or disliked?

The opinion of the majority is that covering the shoulders during prayer is a sunnah (recommended act) and not an obligation, and that prayer performed in a garment that does not cover most of one's shoulders is valid. This is the more preponderant view. The Hanbali school, however, considers the obligatory prayer invalid in this case. Imam An-Nawawi mentioned that there are two narrations from Imam Ahmad: one stating that it is not obligatory in either obligatory or supererogatory prayers, which is also the view of Imam Malik, Imam Ash-Shafi'i, Imam Abu Hanifa, and the majority of early and later scholars. Sheikh Al-Uthaymeen preferred this view, that covering one's shoulders is a sunnah and not an obligation. Therefore, prayer performed in such a garment is disliked but not invalid. It is, however, better to strive to avoid scholarly differences.