The Messenger of Allah ﷺ said: Three things one is not allowed to do: supplicating Allah specifically for himself and ignoring others while leading people in prayer; if he did so, he deceived them; looking inside a house before taking permission: if he did so, it is as if he entered the house, saying prayer while one is feeling the call of nature until one eases oneself.  

قَالَ رَسُولُ اللَّهِ ﷺ ثَلاَثٌ لاَ يَحِلُّ لأَحَدٍ أَنْ يَفْعَلَهُنَّ لاَ يَؤُمُّ رَجُلٌ قَوْمًا فَيَخُصُّ نَفْسَهُ بِالدُّعَاءِ دُونَهُمْ فَإِنْ فَعَلَ فَقَدْ خَانَهُمْ وَلاَ يَنْظُرُ فِي قَعْرِ بَيْتٍ قَبْلَ أَنْ يَسْتَأْذِنَ فَإِنْ فَعَلَ فَقَدْ دَخَلَ وَلاَ يُصَلِّي وَهُوَ حَقِنٌ حَتَّى يَتَخَفَّفَ  

the Prophet said: "It is not allowed for a man to look into the interior of a man's house until he has been given permission, for if he looks, then he has entered. And one who leads people (in Salat) should not supplicate for himself alone with the exclusion of his congregation. If he does, then he has betrayed them. And one is not to stand for Salat while he has to urinate."  

عَنْ رَسُولِ اللَّهِ ﷺ قَالَ لاَ يَحِلُّ لاِمْرِئٍ أَنْ يَنْظُرَ فِي جَوْفِ بَيْتِ امْرِئٍ حَتَّى يَسْتَأْذِنَ فَإِنْ نَظَرَ فَقَدْ دَخَلَ وَلاَ يَؤُمَّ قَوْمًا فَيَخُصَّ نَفْسَهُ بِدَعْوَةٍ دُونَهُمْ فَإِنْ فَعَلَ فَقَدْ خَانَهُمْ وَلاَ يَقُومُ إِلَى الصَّلاَةِ وَهُوَ حَقِنٌ قَالَ وَفِي الْبَابِ عَنْ أَبِي هُرَيْرَةَ وَأَبِي أُمَامَةَ