Narrated Ubaidullah: Ibn `Abbas said, "Why do you ask the people of the scripture about anything while your Book (Qur'an) which has been revealed to Allah's Messenger (ﷺ) is newer and the latest? You read it pure, undistorted and unchanged, and Allah has told you that the people of the scripture (Jews and Christians) changed their scripture and distorted it, and wrote the scripture with their own hands and said, 'It is from Allah,' to sell it for a little gain. Does not the knowledge which has come to you prevent you from asking them about anything? No, by Allah, we have never seen any man from them asking you regarding what has been revealed to you!"
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا إِبْرَاهِيمُ، أَخْبَرَنَا ابْنُ شِهَابٍ، عَنْ عُبَيْدِ اللَّهِ، أَنَّ ابْنَ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ كَيْفَ تَسْأَلُونَ أَهْلَ الْكِتَابِ عَنْ شَىْءٍ، وَكِتَابُكُمُ الَّذِي أُنْزِلَ عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم أَحْدَثُ، تَقْرَءُونَهُ مَحْضًا لَمْ يُشَبْ وَقَدْ حَدَّثَكُمْ أَنَّ أَهْلَ الْكِتَابِ بَدَّلُوا كِتَابَ اللَّهِ وَغَيَّرُوهُ وَكَتَبُوا بِأَيْدِيهِمُ الْكِتَابَ وَقَالُوا هُوَ مِنْ عِنْدِ اللَّهِ. لِيَشْتَرُوا بِهِ ثَمَنًا قَلِيلاً، أَلاَ يَنْهَاكُمْ مَا جَاءَكُمْ مِنَ الْعِلْمِ عَنْ مَسْأَلَتِهِمْ، لاَ وَاللَّهِ مَا رَأَيْنَا مِنْهُمْ رَجُلاً يَسْأَلُكُمْ عَنِ الَّذِي أُنْزِلَ عَلَيْكُمْ.
sunnah.com