What is the authenticity of the narration that whoever recites a thousand verses will be written among the "Muqanṭirīn" (those given a huge reward), and does this imply the desirability of completing the recitation of the Holy Quran every six days?

The hadith refers to the reward for reciting ten, one hundred, or one thousand verses, and what is meant by "reciting" is the night prayer. The term "al-muqanṭarīn" signifies a great reward. Scholars have not inferred from this hadith the desirability of completing the Quran in six nights. Rather, it indicates the desirability of reciting the mentioned number of verses, and this reward is attained by those who recite short verses. As for the recommended duration for completing the Quran, it is derived from other hadiths, such as the hadith of Abdullah ibn Amr, to whom the Prophet, peace and blessings be upon him, specified completing the Quran in a month, and he allowed him to do it in three nights as a minimum. The summary is that the duration varies according to individuals and their circumstances. For those who are people of understanding and contemplation or have important tasks, it is desirable for them to limit themselves to an amount that does not impair contemplation. For those who are not, it is desirable for them to recite more, as long as it does not lead to boredom.