Yawning Can Invalidate the Prayer!

[dkSadiq.ibn.Owodunni]

An important issue about how yawning in the salaah (prayer) can invalidate it is mentioned in this thread on Sahab.net - may Allah reward the one who posted it:

مسألة مهمة قَلَّ من يَتَطرق لها (التثاؤب قد يبطل الصلاة)
http://www.sahab.net/forums/index.php?showtopic=121758

Here's the Summary mentioned at the top of the post: (see the link above for the rest of the post including the ahadeeth regarding the issue and the speech of some of the Salaf - rahimahumullaah):

فالمسألة باختصار:

أن الذي يتثائب عموما وفي الصلاة خصوصا مأمور بالكظم (رد التثاؤب) ما استطاع، وإن مما يؤمر به المتثائب -أيضا- الإمساك عن القراءة لئلا يُسْقِطَ بعض الحروف أو الكلمات، ومعلوم أنَّ الفاتحة ركنٌ من أركان الصلاة، ويجب أن يقرأها المصلي مراعيًا حروفَها وكلماتِها، فلو أَسْقَطَ حرفًا أو خَفَّف شدةً أو أخطأ خطئًا يُغَيِّر المَعْنى مع صِحة لسانه ولم يَسْتَدرِك ذلك الخطأ بطلت صلاته.

والمُتَثَائِب إذا قرأ حَالَ تَثَاؤبه فقد يُسْقِطُ -في الغالب- شيئًا مِن الحروف أو حتى الكلمات فتَخْتَل صلاته إنْ كان هذا السَقْطُ في الفاتحة، فينبغي التنبه لهذا الأمر.

Translation of the Summary (checked & corrected by bro. Moosaa Richardson - may Allaah reward him):

The person who is yawning is, in general and especially in the Salaah, ordered to restrain [i.e. hold back] his yawning as much as he can. Also, from among the things the one who is yawning is ordered with, is to restrain from recitation [while he is yawning] so that some words or letters are not omitted [meaning: he does not actually pronounce the letters or words].

It is known that [reciting] al-Faatihah is a pillar of the prayer and it is obligatory upon the one praying to recite it paying attention to [the correct recitation of] its letters and words. So, if a letter is omitted or a shaddah (ّ_) is lightened or a mistake is made such that the meaning changes while the person's tongue is sound [meaning: his tongue is not a reason for the mistake, rather, he is able to recite it correctly], and he doesn't correct that mistake, the prayer becomes invalid (baatil).

And the one who is yawning, if he recites while he is yawning, then - in most cases - some letters or even words would be omitted and his prayer would be disrupted if this omission is in al-Faatihah - so special attention should be given to this matter.