The Messenger of Allah ﷺ was more particular about observing the supererogatory rak'ahs before the dawn prayer than about observing any of the other supererogatory prayers. (Using translation from Abū Dāʾūd 1254)
لَمْ يَكُنْ رَسُولُ اللهِ ﷺ عَلَى شَيْءٍ مِنَ النَّوَافِلِ أَشَدَّ مُعَاهَدَةً مِنْهُ عَلَى الرَّكْعَتَيْنِ قَبْلَ الصُّبْحِ