In a supplication, an imperative expresses a respectful request.
اللَّهُمَّ اغْفِرْ لِي وَلِوَالِدَيَّ وَلِلْمُؤْمِنِينَ
O Allah, forgive me, my parents and the believers.
رَبِّ اغْفِرْ وَارْحَمْ وَأَنْتَ خَيْرُ الرَّاحِمِينَ
My Lord, forgive and have mercy; You are the best of those who show mercy.