Supplication in prostration has no fixed limit

Question:
The hadith is authentic. The Prophet (peace and blessings be upon him) said: So, if I increase my supplication, for example: “O Allah, forgive me, have mercy on me, guide me, grant me well-being, and provide for me” — during prostration and during the prayer — does this affect my prayer? And does the supplication mentioned by the noble Messenger (peace and blessings be upon him) in prostration have an effect on the prayer, or should I supplicate with what benefits me in matters of life and death? And is it permissible for me to supplicate, for example, by asking for healing from an illness that has befallen me?

Answer:
The hadith is general, and it is an authentic hadith narrated by Imam Muslim in his Sahih from Abu Hurayrah (may Allah be pleased with him) from the Prophet (peace and blessings be upon him) that he said: And Muslim also narrated in his Sahih from Ibn Abbas (may Allah be pleased with him) from the Prophet (peace and blessings be upon him) that he said: meaning, it is likely that it will be answered for you.
So, supplication in prostration is prescribed. One should increase in it, and it has no fixed limit. Rather, the servant supplicates with what Allah has made easy for him according to his need. However, if he supplicates with the supplications narrated from the Prophet (peace and blessings be upon him), that is better.
And among his (peace and blessings be upon him) supplications in prostration: It was narrated by Imam Muslim in the Sahih.
As for the supplication mentioned by the questioner, that is between the two prostrations, and it is his saying (peace and blessings be upon him): So, from Ibn Abbas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) used to supplicate with this between the two prostrations. If he supplicates with it in prostration, or at the end of the tashahhud, or supplicates with other needs of his, there is no harm, such as: “O Allah, heal me from my illness,” “O Allah, provide me with a righteous wife,” “O Allah, make easy for me righteous offspring.” This and the like of it is permissible. The Messenger (peace and blessings be upon him) did not specify one supplication over another, but rather he said: And that encompasses the narrated supplications and others, as mentioned previously. There is no difference in this between the obligatory prayer and the voluntary prayer, due to the generality of the two hadiths mentioned. And success is from Allah.