"When the Prophet (S) did not pray at night because he was prevented from it by sleep or being sleepy then he would pray twelve Rak'ah during the daytime."  

كَانَ النَّبِيُّ ﷺ إِذَا لَمْ يُصَلِّ مِنَ اللَّيْلِ مَنَعَهُ مِنْ ذَلِكَ النَّوْمُ أَوْ غَلَبَتْهُ عَيْنَاهُ صَلَّى مِنَ النَّهَارِ ثِنْتَىْ عَشْرَةَ رَكْعَةً