Is there a clear, authentic text that prohibits masturbation, apart from the interpretations of the verses in Surat Al-Mu'minun, especially given Sheikh Ali Al-Tantawi's statement that there is no such text, and the view of the Hanafis and Imam Ahmad's Musnad permitting it for fear of falling into hardship?

Imam Ahmad did not permit masturbation, even for those who feared committing zina (unlawful sexual intercourse). He held two views on the matter: one of prohibition (tahrim) and another of disliking (karaha). As for the Hanafis, they permitted it under three conditions: that the man is not married, that he genuinely fears falling into zina, and that his intention is not to achieve pleasure but to alleviate the intensity of sexual urge. A thing is deemed prohibited if its harm is medically proven, and the harm of masturbation has been established. Masturbation is permissible only when there is a fear of falling into zina, as it involves committing the lesser of two harms. It is sufficient for the prohibition of masturbation that it is not permissible except when there is a fear of zina. The existence of prohibition does not require an explicit verse or an explicit authentic hadith.