Sahih al-Bukhari 1031
In-book no 1031وَقَالَ أَبُو أُسَامَةَ حَدَّثَنَا هِشَامٌ، قَالَ أَخْبَرَتْنِي فَاطِمَةُ بِنْتُ الْمُنْذِرِ، عَنْ أَسْمَاءَ، قَالَتْ فَانْصَرَفَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَقَدْ تَجَلَّتِ الشَّمْسُ فَخَطَبَ، فَحَمِدَ اللَّهَ بِمَا هُوَ أَهْلُهُ ثُمَّ قَالَ " أَمَّا بَعْدُ ".
And this was narrated by Asma' who said, "Allah's Messenger (ﷺ) finished the eclipse prayer and by then the sun (eclipse) had cleared. Then he delivered the Khutba (religious talk) and praised Allah as He deserved and then said Amma ba'du."