Teaching religious knowledge and giving religious verdicts in a masjid

Narrated Nafi:

'Abdullah bin 'Umar said: "A man got up in the mosque and said: O Allah's Apostle 'At which place you order us that we should assume the Ihram?' Allah's Apostle replied, 'The residents of Medina should assure the Ihram from Dhil-Hulaifa, the people of Syria from Al-Ju,hfa and the people of Najd from Qarn." Ibn 'Umar further said, "The people consider that Allah's Apostle had also said, 'The residents of Yemen should assume Ihram from Yalamlam.' " Ibn 'Umar used to say, "I do not: remember whether Allah's Apostle had said the last statement or not?"

حَدَّثَنِي قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا اللَّيْثُ بْنُ سَعْدٍ، قَالَ حَدَّثَنَا نَافِعٌ، مَوْلَى عَبْدِ اللَّهِ بْنِ عُمَرَ بْنِ الْخَطَّابِ عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ،. أَنَّ رَجُلاً، قَامَ فِي الْمَسْجِدِ فَقَالَ يَا رَسُولَ اللَّهِ، مِنْ أَيْنَ تَأْمُرُنَا أَنْ نُهِلَّ فَقَالَ رَسُولُ اللَّهِ ﷺ " يُهِلُّ أَهْلُ الْمَدِينَةِ مِنْ ذِي الْحُلَيْفَةِ، وَيُهِلُّ أَهْلُ الشَّأْمِ مِنَ الْجُحْفَةِ، وَيُهِلُّ أَهْلُ نَجْدٍ مِنْ قَرْنٍ ". وَقَالَ ابْنُ عُمَرَ وَيَزْعُمُونَ أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ " وَيُهِلُّ أَهْلُ الْيَمَنِ مِنْ يَلَمْلَمَ ". وَكَانَ ابْنُ عُمَرَ يَقُولُ لَمْ أَفْقَهْ هَذِهِ مِنْ رَسُولِ اللَّهِ ﷺ.