The Prophet ﷺ said: Prayer is to be offered in two rak'ahs; and you should recite the tashahhud at the end of two rak'ahs, and express your distress and humility and raise your hands and say praying: O Allah, O Allah. He who does not do so does not offer a perfect prayer. Abu Dawud was asked about offering prayer at night in two rak'ahs. He said: They may be two if you like and four if you like.  

عَنِ النَّبِيِّ ﷺ قَالَ الصَّلاَةُ مَثْنَى مَثْنَى أَنْ تَشَهَّدَ فِي كُلِّ رَكْعَتَيْنِ وَأَنْ تَبَاءَسَ وَتَمَسْكَنَ وَتُقْنِعَ بِيَدَيْكَ وَتَقُولَ اللَّهُمَّ اللَّهُمَّ فَمَنْ لَمْ يَفْعَلْ ذَلِكَ فَهِيَ خِدَاجٌ سُئِلَ أَبُو دَاوُدَ عَنْ صَلاَةِ اللَّيْلِ مَثْنَى قَالَ إِنْ شِئْتَ مَثْنَى وَإِنْ شِئْتَ أَرْبَعًا  

“The Messenger of Allah ﷺ said: ‘The night prayers are (to be offered) two by two. Say the Tashah-hud after each two Rakʿah, and raise your hands in all humility like one who is poor and needy and say: ‘Allāhummaghfir lī (O Allah, forgive me).’ And whoever does not do that, it is imperfect.’”  

رَسُولُ اللَّهِ ﷺ صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى وَتَشَهَّدُ فِي كُلِّ رَكْعَتَيْنِ وَتَبَاءَسُ وَتَمَسْكَنُ وَتُقْنِعُ وَتَقُولُ اللَّهُمَّ اغْفِرْ لِي فَمَنْ لَمْ يَفْعَلْ ذَلِكَ فَهِيَ خِدَاجٌ  

[Machine] Narrated by the Prophet ﷺ, he said, "The prayer is performed in pairs, and the testimony of faith is recited in every two units of prayer. It begins with takbir (saying Allahu Akbar), and ends with taslim (saying As-Salamu Alaykum). The hands are held together in a specific manner, and you say, 'O Allah, O Allah.' Whoever does not do this, then it is deficient and lacking." Hajjaj said, "And the hands are held together."  

عَنِ النَّبِيِّ ﷺ قَالَ الصَّلَاةُ مَثْنَى مَثْنَى وَتَشَهَّدُ فِي كُلِّ رَكْعَتَيْنِ وَتَبَأَّسُ وَتَمَسْكَنُ وَتُقْنِعُ يَدَكَ وَتَقُولُ اللهُمَّ اللهُمَّ فَمَنْ لَمْ يَفْعَلْ ذَلِكَ فَهِيَ خِدَاجٌ وَقَالَ حَجَّاجٌ وَتُقْنِعُ يَدَيْكَ  

“The Messenger of Allah ﷺ said: ‘The night prayers are (to be offered) two by two. Say the Tashah-hud after each two Rakʿah, and raise your hands in all humility like one who is poor and needy and say: ‘Allāhummaghfir lī (O Allah, forgive me).’ And whoever does not do that, it is imperfect.’” (Using translation from Ibn Mājah 1325)   

أَنَّ النَّبِيَّ ﷺ قَالَ الصَّلَاةُ مَثْنَى مَثْنَى وَتَشَهَّدُ وَتُسَلِّمُ فِي كُلِّ رَكْعَتَيْنِ وَتَبَأَّسُ وَتَمَسْكَنُ وَتُقْنِعُ يَدَيْكَ وَتَقُولُ اللهُمَّ اللهُمَّ فَمَنْ لَمْ يَفْعَلْ ذَلِكَ فَهِيَ خِدَاجٌ  

“The Messenger of Allah ﷺ said: ‘The night prayers are (to be offered) two by two. Say the Tashah-hud after each two Rakʿah, and raise your hands in all humility like one who is poor and needy and say: ‘Allāhummaghfir lī (O Allah, forgive me).’ And whoever does not do that, it is imperfect.’” (Using translation from Ibn Mājah 1325)   

عَنْ رَسُولِ اللهِ ﷺ قَالَ الصَّلَاةُ مَثْنَى مَثْنَى وَتَشَهَّدُ فِي كُلِّ رَكْعَتَيْنِ وَتَبَاءَسُ وَتَمَسْكَنُ وَتُقْنِعُ يَدَيْكَ وَتَقُولُ اللهُمَّ اللهُمَّ فَمَنْ لَمْ يَفْعَلْ ذَلِكَ فَهِيَ خِدَاجٌ  

"الصَّلاةُ مَثْنَى مَثنَى، أَن تَشَهَّدَ في كل ركعتين أن تَبَاءَسَ وتَمَسْكَنَ وَتُقْنِعَ بِيَدَيكَ، وَتَقُولَ: اللَّهُمَّ اللَّهُمَّ، فَمَنْ لَمْ يَفْعَلْ ذَلِكَ فَهُوَ خِدَاجُ".  

"صَلاةُ اللَّيلِ مَثْنَى مَثْنَى وتَشَهَّدْ في كُلِّ رَكعَتَين وتَبَأسْ وتَمسْكنْ وَتَقنَعْ وَتَقُولُ: اللهم اغْفِر لي فَمَنَ لم يَفْعَلْ ذَلِكَ فِهَى خِدَاجٌ".