Fatwas of Nur `Ala Al-Darb
Q: What is the difference between Tawassul and Wasilah?
A: Tawassul (supplicating to Allah in the name of …/by virtue of the status of…) is the supplications recited by a person. It is a kind of supplication. One can say, “I invoke You by Your Names.” This is a sort of Tawassul. Also, one may say, “I invoke You by my faith in You.” This is also a way of Tawassul. Here the Wasilah (the means of approach to Allah) is faith, piety and Allah’s Most Beautiful Names. You are the person practicing Tawassul. The Tawassul itself is your supplications. Wasilah refers to the words used in your supplications. When you say, “O Allah! I invoke You by Your Most Beautiful Names and Sublime Attributes to forgive me,” you are the person practicing Tawassul through this supplication. The Wasilah or the means of approach to Allah here is His Names and Attributes. Allah’s Names and Attributes are called Wasilah. This means that supplicating to Allah by His Names and Attributes is a sort of Wasilah. The wording of supplication is called Tawassul. It is a sort of supplicating to Allah by faith, by Allah’s Names and Attributes, or by one’s good deeds.
Source: alifta.net : Browse by Volume Number > Volume 2 > Chapter on Tawassul