Quran 33:56 states that God and the angels send blessings on the Prophet and instructs believers to do likewise, a formulation classical exegetes found genuinely puzzling in one specific respect: ordinary human blessing implies asking for something on behalf of a recipient who lacks it, but God is not usually described in Islamic theology as lacking anything to bestow, so commentators have offered differing explanations of what divine salah upon the Prophet actually consists of, some reading it as God's mercy and praise made manifest, others as God elevating the Prophet's rank and reputation among creation, rather than a literal petition of the kind human blessing normally implies.
Beyond the basic Quranic instruction, an entire genre of extended salawat texts developed over the centuries, most famously the Dala'il al Khayrat, a substantial fifteenth century collection compiled by the North African Sufi Muhammad al Jazuli, organizing an elaborate set of invocations of blessing on the Prophet for daily recitation across the week, which became and remains one of the most widely copied and recited devotional books in the Islamic world independent of the single Quranic verse that originally commands the practice. A specific, shorter formula called the Salat al Ibrahimiyya, invoking blessing on Muhammad in comparison with Abraham, is also recited within the fixed sitting portion, the tashahhud, of the obligatory ritual prayer itself, making some form of salawat a mandatory element of the five daily prayers rather than only an optional devotional extra.