Sahih Al Bukhari Hadith Number 753

Narrated Ibn `Umar: The Prophet (peace be upon him) saw expectoration in the direction of the Qibla of the mosque while he was leading the prayer, and scratched it off. After finishing the prayer, he said, “Whenever any of you is in prayer he should know that Allah is in front of him. So none should spit in front of him in the prayer.”

10  Call to Prayers (Adhaan)
Hadith number 753
Volume no 1
Chapter: 94 ( Is it permissible to one to look around in Salat (prayer) if something happens to one? Or can one look at something like expectoration in the directn of the Qiblah?)