'A'isha reported that the Apostle ﷺ was not so much particular about observing supererogatory rak'ahs as in case of the two rak'ahs of the dawn prayer.
أَنَّ النَّبِيَّ ﷺ لَمْ يَكُنْ عَلَى شَىْءٍ مِنَ النَّوَافِلِ أَشَدَّ مُعَاهَدَةً مِنْهُ عَلَى رَكْعَتَيْنِ قَبْلَ الصُّبْحِ