While the Messenger of Allah ﷺ was praying, he heard a child crying, so he shortened his prayer. We thought he made it brief because of the child, since the child's mother was praying with us.
حدثنا ابن أبي عدي عن حميد
بينما رسول الله ﷺ يصلي إذ سمع بكاء صبي فتجوز في صلاته فظننا أنه إنما خفف من أجل الصبي أن أمه كانت في الصلاة
Its chain of transmission is sahih, previously mentioned at 12812.