Did Imam Abu Hanifa al-Nu'man say that the Hadd (prescribed punishment) is not obligatory for one who has sexual intercourse with his mother by contract, knowing its prohibition, and is his statement recorded in the books of Ahl al-Sunnah wal-Jama'ah?

Abu Hanifa was a scholar, a jurist, and an Imam; he erred and he was correct. Regarding the issue you mentioned, we clarified in Fatwa no. 94238 that he does not rule permissible marriage to محارم (unmarriageable kin). Rather, his discourse is about the establishment of شبهة (doubt/quasisuspect) for someone who marries a woman he is not permitted to marry, and legal punishments are averted by doubts. The majority may disagree with his opinion on this, and the problem is not in the disagreement, but in denigrating him, even though he has a strong point of consideration. As for those who malign Abu Hanifa, they may also malign those greater than him, such as the Companions of the Prophet, peace and blessings be upon him, and their goal is to disparage the Ahlus-Sunnah (Sunnis).