al-Muhaajir ibn Habeeb said:

((‘Eesaa ibn Maryam used to say:

“Indeed whoever prays and fasts, but does not leave off sinning, then it is written that he is a liar”)).

Siyar A'laam an-Nubalaa. - Volume 13, Page 196

Ref: Fatwa-Online

Shaykh Abdul-Azeez ibn Baaz said:

"...many hundreds of students from numerous Muslim nations worldwide have graduated from the University, and have returned to those communities and other than them - teaching the people the good and guiding them to that which is correct."

Ref: The Islaamic University of Madeenah