Patterns/Marks In the Clothing: Simple Clothing Preferred
Hadith - Sunan of Abu Dawood, #4041, Narrated Aisha, Ummul Mu'minin, r.a.
The Apostle of Allah (peace be upon him) once prayed wearing a garment having marks. He looked at its marks. When he saluted, he said: Take this garment of mine to AbuJahm, for it turned my attention just now in my prayer, and bring a simple garment without marks.
Hadith - Muwatta 3.72 - Looking in the Prayer at What Distracts You From It
Yahya related to me from Malik from AIqama ibn Abi AIqama from his mother that A'isha, the wife of the Prophet, may Allah bless him and grant him peace, said, "Abu Jahm ibn Hudhayfa gave the Messenger of Allah, may Allah bless him and grant him peace, a fine striped garment from Syria and he did the prayer in it. When he had finished he said, 'Give this garment back to Abu Jahm. I looked at its stripes in the prayer and they almost distracted me.' "
Allaah hu alim.