Sahih Al Bukhari Hadith Number 724

Narrated Anas bin Malik: I arrived at Medina and was asked whether I found any change since the days of Allah’s Messenger (peace be upon him). I said, “I have not found any change except that you do not stand in alignment in your prayers.”

10  Call to Prayers (Adhaan)
Hadith number 724
Volume no 1
Chapter: 75 (The sin of a person who does not complete the rows (who is out of alignment) for the prayer)