What is the ruling on reciting the poetic verse: "Seek intercession through the Prophet, for every hardship is eased when intercession is sought through the Prophet," along with verifying the authenticity of its attribution to Ali ibn Abi Talib, and are there any scriptural texts that negate it?

The verse mentioned in the question, attributed to Ali ibn Abi Talib, may Allah be pleased with him, is not authentically reported from him, and its content contradicts the permissible forms of tawassul (seeking nearness to Allah through an intermediary). Permissible tawassul falls into three categories:

1. Seeking nearness to Allah through His Names and Attributes: As Allah the Almighty says: ﴿And to Allah belong the best names, so invoke Him by them.﴾ [Al-A'raf: 180]. 2. Seeking nearness to Allah through righteous deeds: Such as seeking nearness through faith. An example of this is the hadith of the three men upon whom a rock fell, and they supplicated to Allah through their righteous deeds. 3. Seeking nearness to Allah through the supplication of a righteous person: As Umar, may Allah be pleased with him, did when he sought rain through Al-Abbas, may Allah be pleased with him, saying: "O Allah, we used to seek nearness to You through our Prophet, and You would grant us rain. And now we seek nearness to You through the uncle of our Prophet, so grant us rain." The meaning is that they used to ask the Prophet, peace and blessings be upon him, for supplication, and after his death, they asked his uncle Al-Abbas for it.

As for impermissible tawassul, it includes seeking nearness through someone's essence (dhat), status (jah), or sanctity (hurmah), like the verse mentioned. There is no sound and explicit evidence to support this type. The hadiths reported in this regard are either authentic but not explicit, or inauthentic and false, such as the hadith: "Seek nearness through my status, for my status with Allah is great."