What is the authenticity of the hadith regarding the prayer of need?

Question:
Is the hadith narrated by Ahmad regarding the prayer of need authentic or not?

Answer:
Yes, Ahmad (may Allah have mercy on him) and others narrated it with a valid chain from Ali (may Allah be pleased with him) from al-Siddiq (may Allah be pleased with him) that the Messenger (peace and blessings be upon him) said: or as he (peace and blessings be upon him) said.
This is authentic and established, and it is one of the known means. If a person sins and does something that Allah dislikes, then he purifies himself and prays two rak'ahs—the prayer of repentance—then asks his Lord and seeks His forgiveness, he is likely to be granted repentance, as Allah has promised him that.
The hadith of the prayer of istikharah is also called the prayer of need; because istikharah is for matters that concern a person, it is prescribed for him to pray two rak'ahs and seek Allah's choice in that matter.