I think you may find it the following question and answer passage by Ottoman Scholar Bediuzzaman.
Question: What is the best way believers can pray for one another?
T h e A n s w e r : It has to be within the bounds of what is acceptable, for supplications become acceptable under certain conditions; their acceptability increases as these conditions are fulfilled. For instance, when supplications are to be made, a person should be purified spiritually by seeking forgiveness; then he should recite benedictions (salawat) for the Prophet (PBUH), an acceptable prayer, and following his supplication, he should again recite the salawat. For a prayer offered between two such acceptable prayers itself becomes acceptable; as is praying for another without their knowledge (بِظَهْرِ الْغَيْبِ) ; and are the traditional supplications and prayers in the Qur’an and Hadiths. For example:
اَللّهُمَّ اِنِّى اَسْئَلُكَ الْعَفْوَ وَ الْعَافِيَةَ لِى وَ لَهُ فِى الدِّينِ وَ الدُّنْيَا وَ اْلآخِرَةِ
رَبَّنَا آتِنَا فِى الدُّنْيَا حَسَنَةً وَفِى اْلآخِرَةِ حَسَنَةً وَ قِنَا عَذَابَ النَّارِ
"O Allah! I beseech You to bestow forgiveness and well-being on me and on so-and-so in religion, this world, and the hereafter. O our Sustainer! Give us good in this world and good in the hereafter, and defend us from the torment of the Fire."
General supplications like these which are offered sincerely, and with humility and tranquillity of heart; and following the five daily prayers, and the morning prayer in particular; and in holy places, and mosques in particular; and on Fridays, and particularly during ‘the hour when prayers are answered;’ and during the three months of Rajab, Sha‘ban, and Ramadan, and on the well-known holy nights, such as the Prophet’s birthday and Ragha’ib, and on the Night of Power in particular - it is to be strongly hoped from Divine mercy that such supplications will be accepted. The results of such acceptable prayers are either seen exactly as wished in this world, or they are accepted in respect of the eternal life in the hereafter of the one who offered them. That is to say, if what was sought does not occur exactly as wished, it may not be said that the prayer was not accepted, but that it was accepted in a better form.