The Letter Sad 38:70. Juz 23, page 457.
إِن يُوحَىٰٓ إِلَىَّ إِلَّآ أَنَّمَآ أَنَا۠ نَذِيرٌ مُّبِينٌ٧٠
It is revealed unto me only that I may be a plain warner.
Sad 38:70, translated by Marmaduke Pickthall