What is meant by "the science of the tongue" (linguistics) and "knowledge of Allah," and is "knowledge of Allah" the correct creed, and what is the meaning of "the greatest knowledge is the knowledge of the heart, which is knowledge of Allah, the Exalted, and knowledge of Allah's command, if it does not lead to Him, the Glorified and Exalted, and to knowledge of Him, then it is a burden upon its possessor"?

Linguistics is merely information that does not revive the heart, nor purify the soul, nor affect behavior, nor lead to action. Whereas the beneficial knowledge that leads to action and necessitates the humility of the heart is knowledge of Allah, and knowing His names and attributes, then knowing His promise and His threat, then knowledge of Allah's rulings and what He loves and is pleased with. So, knowledge of Allah is the correct creed built upon knowing Allah the Almighty, and it is the best knowledge absolutely, and by it the heart is rectified. And knowledge of Allah's command is sought seeking Allah's pleasure, otherwise it would be a burden upon its owner.