ENOfficial
‘Uthman b. ‘Affan reported God’s Messenger as saying, “If the adhan is called when anyone is in the mosque and he goes out for any other reason than some necessary purpose, not intending to return, he is a hypocrite.” Ibn Majah transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَنْ عُثْمَانَ بْنِ عَفَّانَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنْ أَدْرَكَهُ الْأَذَانُ فِي الْمَسْجِدِ ثُمَّ خَرَجَ لَمْ يَخْرُجْ لِحَاجَةٍ وَهُوَ لَا يُرِيدُ الرّجْعَة فَهُوَ مُنَافِق» . رَوَاهُ ابْن مَاجَه
sunnah.com