ONE SHOULD SAY: I seek Your forgiveness. Praise be to Allah, Who has removed from me impurity and given me good health. [1].
Ghufrānak, al-ḥamdu li-llāhi-lladhī adhhaba ‘anni-l-adhā wa ‘āfānī.
It is recorded in the Sunans of Abū Dāwūd and at-Tirmidhī that the Messenger of Allah 
used to say: “I seek Your forgiveness.” And an-Nasā’ī and Ibn Mājah narrated the rest.
used to say: “I seek Your forgiveness.” And an-Nasā’ī and Ibn Mājah narrated the rest.And we relate from Ibn ‘Umar 
who reported that when the Messenger of Allah came out of the lavatory he would say: “Praise be to Allah, Who has let me enjoy its taste, made its strength remain in me and removed from me its harm.” [2].Ibn as-Sunnī and aṭ-Ṭabarānī narrated it.
who reported that when the Messenger of Allah came out of the lavatory he would say: “Praise be to Allah, Who has let me enjoy its taste, made its strength remain in me and removed from me its harm.” [2].Ibn as-Sunnī and aṭ-Ṭabarānī narrated it.
Al-ḥamdu li-llāhi-lladhī adhāqanī ladhdhatah, wa abqā fiyya quwwatah, wa dafa‘a ‘annī adhāh.
References
[1] Abū Dāwūd (30), at-Tirmidhī (7), and Ibn Mājah (300), from ‘Ā’ishah 
. Imam an-Nawawī states in al-Majmū‘ that it is ḥasan ṣaḥīḥ.
. Imam an-Nawawī states in al-Majmū‘ that it is ḥasan ṣaḥīḥ.[2] Ibn as-Sunnī (25) and al-Futūḥāt (1/405). Ibn Ḥajar said that its chain contains two weak narrators and a break; nevertheless, there are supporting narrations for this hadith.