What is the meaning of the submission (al-inqiyād) the abandonment of which constitutes disbelief (kufr), according to what was narrated from Ibn Taymiyyah, that faith (al-īmān) is not complete except with affirmation (al-taṣdīq) and submission (al-inqiyād)?

What is meant by submission (al-inqiyād) is obedience to God's command and not being arrogant. As Sheikh al-Islam Ibn Taymiyyah said: "Faith is affirmation, not mere assent. Affirmation includes assenting to information and submitting to commands." God’s words are both information and commands. Information necessitates assent, and commands necessitate submission and surrender. A believer cannot be a believer except by combining both. Whoever abandons submission is arrogant, like Iblis, even if he assents. Disbelief is more general than denial and can be a result of arrogance and injustice. The two testimonies (Shahadatayn) entail assenting to information and submitting to commands.