ENOfficial
Narrated Ibn `Abbas: The Prophet (ﷺ) stood before Musailama (the liar) who was sitting with his companions then, and said to him, "If you ask me for this piece (of palm-leaf stalk), even then I would not give it to you. You cannot avoid what Allah has ordained for you, and if you turn away from Islam, Allah will surely ruin you! "
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو الْيَمَانِ، أَخْبَرَنَا شُعَيْبٌ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي حُسَيْنٍ، حَدَّثَنَا نَافِعُ بْنُ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ وَقَفَ النَّبِيُّ صلى الله عليه وسلم عَلَى مُسَيْلِمَةَ فِي أَصْحَابِهِ فَقَالَ " لَوْ سَأَلْتَنِي هَذِهِ الْقِطْعَةَ مَا أَعْطَيْتُكَهَا، وَلَنْ تَعْدُوَ أَمْرَ اللَّهِ فِيكَ، وَلَئِنْ أَدْبَرْتَ لَيَعْقِرَنَّكَ اللَّهُ ".
sunnah.com