What is the authenticity of the Hadith: "Be earnest in supplication, for whoever knocks frequently at the door is about to have it opened for him"?

The saying: "Strive in supplication, for he who knocks frequently at a door is likely to have it opened for him" has not been authentically reported as a Hadith from the Prophet, peace and blessings be upon him. Rather, Ibn Abi Shaybah and Al-Bayhaqi narrated it as a statement from Abu Al-Darda' with the wording: "And supplicate frequently..."