There are four types Tawassul, according to the meaning of this word, which literally means "seeking a means". Two are permitted and two unlawful.

[1] To call on other than Allah believing that that being has the power to give benefit or harm. This is not just unlawful but also Shirk.

[2] To call on other than Allah (SWT) believing that Allah (SWT) has given over some authority to a certain individual to also benefit or harm. This is also in reality a branch of Shirk.

[3] To ask a person who one believes to be pious and close to Allah to do Dua for you. This also comes under the meaning of Tawassul mentioned above and is permitted by all the scholars.

[4] To call upon Allah (SWT) directly, and at the same time in order to make the Dua more likely to be accepted, to make mention of a good deed one did, the name of a pious person (living or dead) who is close and beloved to Allah (SWT) and also beloved to that person. Thus a person would say: "O Allah fulfil such and such a need for the sake of the Messenger of Allah, peace and blessings be upon him." This type of Tawassul is also permitted by the majority of scholars.

From this we also learn that the propaganda or more precisely ignorance poured out by some people that Tawwasul is Haram and Bidah is far from the truth.

The proofs of the permissibility of types no.3 and 4 are:

The Hadith of the blind man who asked the Messenger of Allah, peace and blessings be upon him, to cure him of his blindness. The Messenger of Allah, peace and blessings be upon him, said: If you have patience you will receive the reward and if you wish I will pray for you. The man chose to be cured. So the Messenger of Allah, peace and blessings be upon him, told him to pray two rakaas and then pray saying the words: O Allah I turn to you with your Prophet.... After saying this prayer his sight was returned to him. This is a famous hadith narrated by many Hadith scholars including Imam .

The other Hadith, is recorded by Imam Bayhaqi in his sunnan. In the time of Uthman r.a. a man had a pressing need for which he was unable to get an audience with the Khalif of the time, Uthman r.a. After many attempts Uthman ibn Hunayf r.a. advised him to do the same as he had seen the blind man do. Thus this man prayed using the same words the blind man did. Soon after that the man was to his shock not only invited to see the Khalif, he had his need met and further promised by Uthman r.a. to never hesitate if he had a need to bring it to him.

This was all the barakah of Tawassul using the name of the Messenger of Allah, peace and blessings be upon him. One will also note that the above incident occurred after the death of the Prophet, peace and blessings upon
him, proving Tawassul even with the dead is permitted.

Another proof for Tawassul is the story in Bukhari about the three young men who were trapped in a cave by a huge rock. They were able to get the rock to move away from the entrance by citing in their duas certain good deeds they had done.