Tariq bin Ashyam (May Allah be pleased with him) reported: Whenever a man entered the fold of Islam, the Prophet (sallallaahu ’alayhi wa sallam) would show him how to perform Salat and then direct him to supplicate: "Allahumm-aghfir li, warhamni, wa-hdini, wa `afini, warzuqni (O Allah! Forgive me, have mercy on me, guide me, guard me against harm and provide me with sustenance and salvation).'''
[Muslim].
In another narration Tariq said: A man came to the Prophet (sallallaahu ’alayhi wa sallam) and said to him: "O Messenger of Allah! What shall I say if I want to pray to my Rubb?'' He (sallallaahu ’alayhi wa sallam) said, "Say: `Allahumma-ghfir li, warhamni, wa `afini, warzuqni (O Allah! Forgive me, have mercy on me, protect me and provide me with sustenance).' Surely, this supplication is better for you in this life and in the Hereafter.''
[Muslim].
In another narration Tariq said: A man came to the Prophet (sallallaahu ’alayhi wa sallam) and said to him: "O Messenger of Allah! What shall I say if I want to pray to my Rubb?'' He (sallallaahu ’alayhi wa sallam) said, "Say: `Allahumma-ghfir li, warhamni, wa `afini, warzuqni (O Allah! Forgive me, have mercy on me, protect me and provide me with sustenance).' Surely, this supplication is better for you in this life and in the Hereafter.''