Reference : Hisn al-Muslim 80

اللّهُـمَّ إِنِّـي أَصْبَـحْتُ أَُشْـهِدُك ،
وَأُشْـهِدُ حَمَلَـةَ عَـرْشِـك ،
وَمَلائِكَتِك ، وَجَمـيعَ خَلْـقِك ،
أَنَّـكَ أَنْـتَ اللهُ لا إلهَ إلاّ أَنْـتَ
وَحْـدَكَ لا شَريكَ لَـك ،
وَأَنَّ ُ مُحَمّـداً عَبْـدُكَ وَرَسـولُـك .
(أربع مرات حينَ يصْبِح أوْ يمسي)
Allāhumma innī aṣbaḥtu ush-hiduka 
wa ush-hidu ḥamalata `arshik, 
wa malā'ikataka wajamī`a khalqik, 
annaka antallāhu lā ilāha illā ant, 
waḥdaka lā sharīka lak, 
wa anna Muḥammadan `abduka wa rasūluk.


O Allah, I have entered a new morning 1 and call upon You and upon the bearers of Your Throne, 
upon Your angels and all creation 
to bear witness that surely You are Allah, there is none worthy of worship but You alone, You have no partners, 
and that Muhammad is Your slave and Your Messenger. 
(Recite four times in Arabic.) 2

Reference:
1 When you say this in the evening you should say, Allāhumma innī amsaytu. . . .: "O Allah, I have ended another day..."
2 "Allah will spare whoever says this four times in the morning or evening from the fire of Hell." Abu Dawud 4/317. It was also reported by Al-Bukhari in Al-'Adab Al-Mufrad, An-Nasa'i in 'Amalul-Yawm wal-Laylah and Ibn As-Sunni. Nasa'i's and Abu Dawud's chains of transmission are good 
(Hasan), Ibn Baz, p. 23.

Chapter: In the morning and evening