I wanted to learn what Ḥadīth Qudsi really is. Are there only forty aḥadīth qudsi? If they are the word of Allah Almighty then why are they not included in the Qur'an? Could you pleae explain the following Ḥadīth from Tirmidhi: O Man devote yourself to My worship, I shall grant you satisfaction of heart and remove your hunger. If, however, you do not do that you shall not be able to kill your hunger even if you worked day and nights." This doe not seem to be the reality in our life. Please clarify this.
Hadith Qudsi is a statement ascribed to the Almighty Allah by the Prophet (sws) other than the Qur'an. We know that the Prophet (sws) was in direct communication with the Almighty Allah. However, these ahadith are not absolutely authentic in their transmission from the Prophet (sws) to us. They are not verbatim and the problems that affect the individual to individual tradition from the Prophet (sws) down to us are also present in these ahadith as well. Therefore, we can discuss and analyze the isnad and the text of any hadith qudsi. There can be spurious hadith qudsi as well.
They are not only forty. There are many some, weak, some sound and some fabrications.
The hadith you have quoted has been declared authentic by authorities. I wonder what is the question in your mind concerning it.