I doubt you will be able to provide overwhelming evidence, since
nobody has done so before, but it will be interesting to see you try.
So your telling my you have read all the books to ever exist in Islamic history and heard all the scholars alive or dead and then you came to that conclusion lets be realistic.
Shafa'a, as in intercession on the day of judgement, is in the Qur'an, so obviously I believe in it. Tawassul and istighatha on the other hand, are neither well supported by the Quran or the ahadith, and in fact seem to contradict those sources.
Good we agree on shafa"a now let’s discuses Tawassul. Lets define it first so where on the same page. Tawassul is anything which
becomes a means to gain nearness to Allah. In its general Islamic meaning, everything which takes us near Our Lord is mediation.
Therefore all good deeds such as faith in Allah and the Prophet (peace be upon them), prayers, fasting, Hajj, and other deeds serve as
mediators that draw us nearer to Allah. There are many ways to get near to him and this is really what where discussing here one of the ways and that’s The Prophets and Imams(AS). In the Holy Qur'an (5:35), it says: "O you who believe! be careful of (your duty to) Allah and seek means of nearness to Him and strive hard in His way that you may be successful." The scholars in exegesis to the above verse of holy Qur'an say that the mediation from Prophets, Imams or the righteous servants of Allah is included in the meaning of mediation. Allama Tabatabai discusses the verse in
Al-Mizan in the following words:
"Al-Qummi has written about the words of Allah: 'O you who believe! Fear Allah and seek means of nearness to Him...' that (the Imam) said, 'Come near Allah through the Imam'... That is, through obedience to the Imam. Thus it is based on the flow of the Qur'an, and applies the verse to its best import... The Leader of the Faithful said about the Divine Word 'and seek means of nearness to Him': 'I am the means of nearness to Him'."
In a lengthy narration known as the Hadith of Wasila, the Prophet is reported to have said, "When you ask from Allah, ask for me the Wasila... It is my rank in the Garden..."
Allama Tabatabai further states: "[we] will find that Wasila is the position of the Prophet in the presence of his Lord, with which he gets nearer to Allah; and joins him there his pure progeny, then the good servants from among his
Ummah. It has also been narrated in some traditions from them that verily the Messenger of Allah adheres to his Lord, and we adhere to him and you adhere to us."
Imam as-Sajjad (peace be upon him) on mediation:
My God, I have no mediation with Thee but the tender acts of Thy clemency, nor any way to come to Thee but the gentle favors of Thy mercy and the intercession of Thy Prophet, the prophet of mercy, who rescued the community from confusion. Make these two my tie to attaining Thy forgiveness and let them take me to triumph through Thy good pleasure! My hope has dismounted in the sacred precinct of Thy generosity, my craving has alighted in the courtyard of Thy munificence. So actualize my expectation from Thee, seal my works with good, and place me among Thy selected friends, those whom Thou hast set down in the midst of Thy Garden, and settled in the abode of Thy honor, whose eyes Thou hast gladdened by gazing upon Thee on the day of meeting Thee, and whom Thou hast made heirs to the sure stations in Thy neighborhood!
O He none more generous than whom is reached by the reachers and none more merciful than whom is found by the aimers! O Best of those with whom the lonely are alone, O Tenderest of those with whom outcasts seek haven! Toward the expanse of Thy pardon have I extended my hand, upon the skirt of Thy generosity have I fastened my grasp! Show me no deprivation and afflict me not with disappointment and loss! O Hearer of supplications! O Most Merciful of the merciful!"
Allah says in the Holy Qur'an, "Oh you who believe: be aware of Allah and seek to Him
theWaseela (intermediate to reach Him)" (5:35). The verse obviously commands the believers to seek intermediates to reach Allah. Why? Because He made the perfect system, and He knows that we reach our perfection by utilizing the system appropriately. Among these "intermediates" are those Allah has chosen to guide us, such as the greatest of Allah's Creation, Muhammad (peace be upon him and his family).
"And if they had – after having done injustice to themselves – come to you (Muhammad) and asked Allah for forgiveness, and the Messenger then would ask Allah to forgive them, they would have found that Allah is Oft-Returning (to Mercy), Merciful” (4:64).
When an aware believer says "Oh Ali!" (s)he is not truly seeking Imam Ali (peace be upon him). Rather, the believer seeks Allah, and because Allah has commanded the believer to seek Him through the chosen intermediates, the believer does not hesitate to do so.
"So what? Are we saying that calling out 'Oh Allah!' is not sufficient?!" No…
but one cannot deny that Allah has commanded us to seek Him in a specific way, i.e. via these intermediates.
I
f one calls out "Oh Ali!" thinking that Imam Ali (peace be upon him) can independently do anything for the person, it is definitely Shirk. Similarly, if one knowingly calls out "Oh Allah!" without seeking Him through the appropriate means –at heart – then such a call cannot be considered true obedience to the Wisest of Planners.
"But God would not punish them while
YOU WERE PRESENT in their midst. Nor would He punish them if they SOUGHT FORGIVENESS" (8:33). In this verse the physical
presence of the holy prophet is equated with Isteghfar (seeking forgiveness) as far as protection from God's punishment is concerned. Thus It is clear that physical proximity
with the holy prophet make potential for us to receive God's grace. To give you another example we read in the holy Qur'an that Prophet. Yousuf

tells his brothers "Take
this shirt of mine and throw it over my father's face: he will recover his sight. Then return to me with all your people" (12:93). Think about this, Ya'ghub

himself is a
prophet and Yousuf's father, why doesn't his own shirt do the same thing? First because the act of recovery is not a function of the shirt, it is God's action, second God's
wants to educate us and tell us that He puts Rahmah (grace) in the physical belongings of his true servants and encourages us to have close and respectful relationships
with them for those relationships make us ready for more Taghva. To encourage this He bestows some special Rahmah in his true servants. Like the one in the physical
presence of the holy prophet and the one in Yousuf's shirt.
The Holy Quran Says
They said, 'Father! Plead {with Allah} for forgiveness of our sins! We have indeed been erring'. He said, 'I shall plead with my Lord to forgive you; indeed He is the All-forgiving, the All-merciful'.[32]
In these verses, the sons of Ya'qub (
'a) resorted to the intermediation of their father. They had committed mistakes so many times; they had annoyed and disturbed two prophets of God (Ya'qub and Yusuf (Joseph) (
'a)), and transgressed the command of God by annoying their parents and telling lies. Since those mistakes required the sons to seek forgiveness, they took their
father as their intercessor; so this action has not been denied or rejected in the Qur'an.
Since God does not reproach the sons of Ya'qub for resorting to two persons of those who are near to Him {
muqarrabun}, it can be concluded that there is nothing wrong in entreating the Prophet (s) especially since the eminence of his rank and the loftiness of his station are not hidden to anyone.
The other verse which may be cited is the following:
Had they, when they wronged themselves, come to you and pleaded Allah for forgiveness, and the Apostle had pleaded for forgiveness for them, they would have surely found Allah All-clement, All-merciful.[33]
It can be deduced from this verse that the intermediation of the Holy Prophet (s) can also be resorted to in asking God for forgiveness of sins.
Anyways sorry if the post is too long but I want to ask you a question to see what you think. In the following verse:
(We revealed to Moses' mother, "Suckle him and then when you fear for him, cast him into the sea. Do not fear or grieve; We will return him to you and make him one of the messengers.") (Al-Qasas 28:7) Allah(SWT) says that he revealed to Prophet Moses(AS)
mother my question is His mother was not a Prophet nor an Imam in what way do you think Allah(swt) revealed to her what to do?
Salam