What constitutes speech that invalidates prayer?

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Speech that invalidates prayer is defined as that which consists of two letters. This is the position held by the companions of our school (Hanafi) and the companions of Al-Shafi'i. Two letters are sufficient to form a word, such as 'ab' (father), 'akh' (brother), or 'dam' (blood). This applies equally to verbs and particles; a word cannot be formed from fewer than two letters. Therefore, if one says the word 'la' (no), which consists of the letters lam and alif, the prayer is invalidated. This view is supported by Jabir ibn Abdullah, 'Ata, Mujahid, Al-Hasan, Qatadah, Al-Nakha'i, Al-Awza'i, Al-Shafi'i, and the Ashab al-Ra'y (People of Opinion). There is no known opposition to this ruling.