What are the types of permissible and forbidden tawassul (seeking nearness to Allah through a means)?

Question:
May Allah reward you, Honorable Shaykh. This questioner asks: What are the types of permissible and forbidden tawassul (seeking nearness to Allah through a means)?

Answer:
Tawassul (seeking nearness to Allah through a means). It is making a means or a way to Allah (Glorified and Exalted is He). This is only done by obeying Allah and the means is the obedience that brings one closer to Allah (Mighty and Majestic) This is the means: obeying Allah (Exalted and Majestic is He), fearing Him, and hoping in Him. This is the correct means: righteous deeds. Tawassul through righteous deeds is prescribed (mashru'), just as the people of the cave, upon whom a rock closed the entrance to the cave and they could not get out, sought nearness to Allah through their righteous deeds. One of them sought nearness through his dutifulness to his parents, and another sought nearness to Allah (Mighty and Majestic) through His mercy regarding forbidden acts; after he had the opportunity to commit them, he left them for the sake of Allah (Mighty and Majestic). His mercy regarding zina (unlawful sexual intercourse); after he had the opportunity, he stood up and left it out of fear of Allah (Glorified and Exalted is He). The third sought nearness to Allah through his preservation of the wages of a worker who was with him; he left and preserved his wages, increasing them for him and keeping them safe until he came and took them. So Allah relieved them and they walked out. This is tawassul to Allah through righteous deeds, and it is prescribed (mashru').
Seeking nearness to Allah through tawhid (the oneness of Allah) is how Yunus (peace be upon him) sought nearness to Allah: He sought nearness through the tawhid of Allah (Glorified and Exalted is He). Seeking nearness through the supplication of the righteous who are present is also prescribed. You come to a righteous man and say to him, "Call upon Allah for me for such and such." This is also prescribed, as evidenced by the fact that when 'Umar (may Allah be pleased with him) and the people faced a drought and sought rain, he asked al-Abbas (may Allah be pleased with him) to call upon Allah for rain because of his kinship with the Messenger of Allah (peace and blessings be upon him). He said, "O Allah, we used to seek nearness to You through Your Prophet when we faced a drought, and You would send us rain. Now we seek nearness to You through the uncle of our Prophet, so send us rain." So al-Abbas stood up and called upon Allah (Mighty and Majestic), and Allah sent them rain. Seeking nearness through the supplication of the righteous who are present and able to call upon Allah (Mighty and Majestic) — these are the types of prescribed tawassul (seeking nearness to Allah through a means). As for the prohibited tawassul, it is seeking nearness to Allah (Mighty and Majestic) through the creation, such as saying, "I ask You by Your Prophet" or "I ask You by Your wali (close friend of Allah) so-and-so." This tawassul is prohibited because it is swearing by Allah using a created being, and this is not permissible. Furthermore, there is no evidence for it, and what has no evidence is not permissible to do. Seeking nearness through the persons of the righteous, or through their status, or through their right, is prohibited tawassul, and it is a means to shirk (associating partners with Allah). Seeking nearness to Allah (Mighty and Majestic) through the dead, or through graves — all of this is either shirk or a means to shirk.