Sayyid Ibn Tawus and Shaykh al-Saduq have both narrated the following on the authority of Jabir ibn ‘Abdullah al-Ansari: I visited the Messenger of Allah (a.s.) on the last Friday of Ramadan. As he saw me, he said: O Jabir, this is the last Friday of Ramadan. You should thus bid farewell to it by saying the following:
اَللّٰھُمَّ لَا تَجْعَلْهُ اٰخِرَ الْعَھْدِ مِنْ صِيَامِنَااِيَّاهُ فَاِنْ جَعَلْتَهٗ فَاجْعَلْنِيْ مَرْحُوْمًا وَّلَا تَجْعَلْنِيْ مَحْرُوْمًا
O Allah, (please) do not make it the last of our fasting in this month, but if You decide so, then (please) make me enjoy (Your) mercy and do not make me deprived (of it).
Verily, whoever says this supplicatory prayer will win one of the two good things; either attaining the next Ramadan or having the forgiveness and mercy of Almighty Allah.