Reference : Hisn al-Muslim 90
أَصْـبَحْنا[أَمْسَـينا] علـى فِطْـرَةِ الإسْلام،
وَعَلـى كَلِـمَةِ الإخْـلاص، 
وَعلـى دينِ نَبِـيِّنا مُحَـمَّدٍ 
وَعَلـى مِلَّـةِ أبينـا إِبْـراهيـمَ 
حَنيـفاً مُسْلِـماً 
وَمـا كـانَ مِنَ المُشـرِكيـن
Aṣbahnā `alā fiṭrati ‘l-Islām, 
wa `alā kalimati ‘l-ikhlās, 
wa `alā dīni nabiyyinā Muḥammadin (ṣallallāhu `alayhi wa sallam), 
wa `alā millati abīnā Ibrāhīm, 
ḥanīfan Musliman 
wa mā kāna mina ‘l-mushrikīn.

We have entered a new day 1 upon the natural religion of Islam, 
the word of sincere devotion, 
the religion of our Prophet Muhammad (peace and blessings of Allah be upon him), 
and the faith of our father Ibrahim. 
He was upright (in worshipping Allah), and a Muslim. 
He was not of those who worship others besides Allah. 2

Reference:
1 When you say this in the evening, you should say: 'Amsaynā `alā fiṭratil-Islām...: "We end this day..."
2 Ahmad 3/406-7, 5/123, An-Nasa'i, 'Amalul- Yawm wal-Laylah (no. 34), 
At-Tirmidhi 4/209.

Chapter: In the morning and evening