Hakim al-Umma Mawlana Ashraf ‘Ali Thanawi (may Allah have mercy on him) said in regards to tajweed, that is, reading the holy Quran with correct pronunciation,

“It is essential (wajib) to make effort in this. Being careless and lazy in it is a sin.”

Bahishti Zewar

Reading Quran al-Karim without proper pronunciation changes the meaning of the text.

Qari Mohammad Rafiq, a senior student of Qari Shaykh Fateh Mohammad Panipati (senior instructor at Darul Uloom Karachi who migrated to and died in radiant city of Medinah) told an individual that teaching the ‘arabic language primer (qa’ida) properly is the most important step in learning recitation of Quran.