It is narrated from Sayyidah Aisha (may Allah be pleased with her) that the Prophet (peace and blessings of Allah be upon him) did not pay more attention to any voluntary prayer than the two rak'ahs before the Fajr prayer.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب الركعتين قبل الفجر وما فيها من السنن / 1109