Du’aa’ during wudu by the status of the Prophet (peace and blessings of Allah be upon him)
Question

I have a habit which I do not know if it is good or bad:  
I ask Allah while washing my feet during wudu’ by the Prophet’s virtue to keep my feet firm on the Siraat. 
Also during the prayer I ask Allah by his Prophet’s virtue to forgive my sins and to have mercy on me. Is this du’a permissible or not?  
I used to make du’a in this way believing that Allah will answer the prayer of who asks him by His beloved Prophet’s virtue, may peace and blessings of Allah be upon him.
Praise be to Allah.Asking Allah to make His slave’s feet steadfast on the Straight Path is a good du`a and there is nothing wrong with it. We ask Allah to make the feet of all of us steadfast. 
But there are two mistakes in this du`a: 
1 – Always reciting it when washing your feet during wudu: 
You know that wudu is an act of worship and that the Muslim does not have the right to change the way an act of worship is done or add to it or take away from it; rather following the Prophet (peace and blessings of Allah be upon him) properly means doing what he did, without adding or taking anything away. 
Ibn Taymiyah (may Allah have mercy on him) said in Majmoo’ al-Fatawa (22/510): 
No one has the right to introduce to the people any kind of dhikr or du`a apart from those that are narrated in the Sunnah, and make them a regular act of worship that the people do all the time, as they do the five daily prayers; rather this is innovation in the religion for which Allah has not given permission. End quote. 
It was not the practice of the Prophet (peace and blessings of Allah be upon him) to say du`a when washing the parts of the body that are washed in wudu. There is a hadith concerning that, but it is not a saheeh narration from the Prophet (peace and blessings of Allah be upon him). 
Al-Haafiz ibn al-Salaah said: 
There is no saheeh hadith concerning that. End quote. It was mentioned thus by al-Haafiz Ibn Hajar in al-Talkhees al-Habeer (1/297). 
Ibn al-Qayyim said in al-Manaar al-Muneef (45): 
As for the mawdoo’ (fabricated) hadith about dhikr when washing each part of the body (in wudu), it is baatil (invalid). End quote. 
Al-Nawawi (may Allah have mercy on him) said of the du`as recited when washing each part of the body (in wudu): The du`a for washing each part of the body (in wudu) has no basis. 
Al-Futoohaat al-Rabbaaniyyah (2/27-29).
 In Fatawa al-Shaykh Muhammad ibn Ibraaheem (2/49): 
Some people think that there is a dhikr for every part of the body (when doing wudu), and some ahaadeeth have been narrated concerning that, but they are not saheeh at all, rather they are false. End quote. 
In Duroos li’l-Shaykh ‘Abd al-‘Azeez ibn Baaz (no. 13, tape 2) it says: 
There is no basis for any of this, and nothing has been narrated in a sound report from the Prophet (peace and blessings of Allah be upon him), so these du`as are not recommended when washing these parts of the body. Rather what is recommended (mustahabb) is two things: Firstly, when starting to do wudu, one should mention the name of Allah; secondly, after finishing wudu one should recite the Shahaadah. This is what is prescribed with regard to wudu. End quote. 
It cannot be said that weak ahaadeeth should be acted upon with regard to good deeds, because there is no consensus on this principle and there are some who disagree with it. Moreover, with regard to acting upon weak ahaadeeth, it is stipulated that they should not be severely weak, and this condition is not met in this case, as was understood by Ibn ‘Allaan in al-Futoohaat al-Rabbaaniyyah (2/29). 
Al-Suyooti (may Allah have mercy on him) wrote an essay on this matter entitled al-Ighda’ ‘an Du`a al-A’daa’, in which he explained how very weak the reports concerning that are, and that they are not fit to be acted upon, even with regard to good deeds. 
See also the answer to question no. 45730. 
2 – As for the second mistake, it is your saying in your du`a, “by the status of the Prophet (peace and blessings of Allah be upon him)”. 
Undoubtedly the status of the Prophet (peace and blessings of Allah be upon him) is great, but Allah has not made seeking to draw near to Him (tawassul) by means of that one of the causes of du`a being answered. 
And the Prophet (peace and blessings of Allah be upon him) – who is the one who did not omit to guide us to anything that is good – did not teach us to seek to draw near to Allah by means of that. 
Hence it is known that this du`a is not prescribed. 
This has already been explained in the answer to question no. 23265.
 So strive to follow the Sunnah of the Prophet (peace and blessings of Allah be upon him) and do not add anything to it or take anything away; keep away from things that have been introduced into the religion, as the Messenger (peace and blessings of Allah be upon him) advised us when he said: “I urge you to adhere to my Sunnah and the sunnah of the rightly guided Khulafa’ (al-Khulafa’ al-Raashideen), and to seize it firmly. Beware of newly-innovated things, for every innovation is a going-astray.” Narrated by Abu Dawood (4607); classed as saheeh by al-Albaani in Saheeh Abi Dawood. 
And Allah knows best.