When sitting between two sujood prostrations #1
An-Nasa'i: 1146, 1666 Abu Dawud: 874
رَبِّ اغْفِرْ لِي رَبِّ اغْفِرْ لِي
Lord, forgive me. My Lord, forgive me.
When sitting between two sujood prostrations
When sitting between two sujood prostrations #2
Ibn Majah: 3845, 1517 At-Tirmidhi: 284
اللَّهُمَّ اغْفِرْ لِي، وَارْحَمْنِي، وَاهْدِنِي، وَاجْبُرْنِي، وَعَافِنِي، وَارْزُقْنِي، وَارْفَعْنِي
O Allah forgive me, have mercy on me, guide me, support me, protect me, provide for me and elevate me.