Tafsir Ibn Kathir -> Surah Al-Furqan -> The Messenger brings Glad Tidings and Warnings

Then Allah tells His Messenger:

﴿وَمَآ أَرْسَلْنَـكَ إِلاَّ مُبَشِّراً وَنَذِيراً ﴾

(And We have sent you only as a bearer of good news and a warner.) meaning, a bringer of good news to the believers, a warner to the disbelievers; bringing good news of Paradise to those who obey Allah, and bringing warnings of a dreadful punishment for those who go against the commandments of Allah.

﴿قُلْ مَآ أَسْأَلُكُمْ عَلَيْهِ مِنْ أَجْرٍ﴾

(Say: "No reward do I ask of you for this...'') `for conveying this message and this warning, I do not ask for any reward from your wealth; I am only doing this for the sake of Allah, may He be exalted.'

﴿لِمَن شَآءَ مِنكُمْ أَن يَسْتَقِيمَ ﴾

(To whomsoever among you who wills to walk straight) (81:28).

﴿إِلاَّ مَن شَآءَ أَن يَتَّخِذَ إِلَى رَبِّهِ سَبِيلاً﴾

(save that whosoever wills, may take a path to his Lord.) means, a way and a methodology to be followed.