(a) Sayyiduna Anas bin Malik (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "I am in prayer and intend to make the recitation in it long, then I hear the sound of a child crying, so I shorten the prayer, feeling the hardship on his mother."
(b) A narration with the same meaning is also reported from Sayyiduna Abu Qatadah al-Ansari (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4043