Kitab Al-Salaah (The book of Prayer)

Things
Which Invalidate The Prayer (Mubdilatu-Salaat)

           
Prayer if performed well with due regard to its conditions, pillars,
duties and preferred acts, truly illuminates the heart and purifies the
soul. It is the means by which man communicates with Allah (subhanahu
wa ta'ala) and therefore, one should keep it free from anything which
would render it invalid. In Arabic Language, the acts which invalidate
the prayer are known as "Mubdillatu-Salaah" and we now list them here
below:

• Speaking or talking in the course of the prayer.
• Laughing in the course of the prayer.
• Eating while praying, even though what is eaten maybe as
  small as a piece of dates.
• Drinking while praying, even though what is drank maybe as
  small as taking only a mouthful.
• If someone in the course of the prayer remembers that he/she
  did not actually perform the ablution (wudhu), then, such a person is
  required to break the prayer and get out to perform Wudhu.
• If a person's ablution (wudhu) gets invalidated in the course
  of the prayer, then the prayer becomes invalid.
• The prayer is also invalidated by carrying out the Rukuu and
  Sujuud postures with haste and without ease. While in prostration,
  bobbing (jerking) up and down like chicken pecking food from the ground
  is not allowed.
• Turning oneself away from the direction of the Qiblah also
  invalidates the prayer.