Supplication for Fridays' Ghusl (Full-Ablution)

Imam Sadiq (A.S) said: whoever performs the full-ablution (Ghosl) on Friday, and then says: 

أَشْهَدُ أَنْ لاَ إِلَهَ إِلّاَ اللهُ وَحْدَهُ لاَ شَرِيكَ لَهُ وَ أَنَّ مُحَمَّداً عَبْدُهُ وَ رَسُولُهُ. اللَّهُمَّ صَلِّ عَلَى مُحَمَّدٍ وَ آلِ مُحَمَّدٍ وَ اجْعَلْنِي مِنَ التَّوَّابِينَ وَ اجْعَلْنِي مِنَ الْمُتَطَهِّرِينَ، 

I testify that there is no god but Allah, He is alone and no one is His partner, and that Muhammad is His servant and prophet. O’ Lord! Send down Your blessings upon Muhammad and his Household, and make me one of those who repent and place me among the purest. 

There will be purity for them until the next Friday. 

Man-La-Yahdhuruh al-Faqih, vol. 1, p. 112

Wasa’il Al-Shi’a, vol. 3, p. 323