What is the authenticity of the Hadith: "Whoever sits in his prayer place where he prayed Fajr, remembering Allah, Glorified be He, praising Him and glorifying Him, until the sun rises, will be like one who has performed Hajj to the House of Allah, and like one who has striven in the way of Allah, the Mighty and Majestic"?

Uncorroborated narrations in "Musnad Zayd" are not reliable because they were transmitted with a very weak chain of narration through 'Amr ibn Khalid al-Wasiti, who was a liar and a fabricator. As for the virtue of sitting for remembrance (dhikr) after Fajr prayer until sunrise, and then praying two rak'ahs, it was mentioned in a hadith by Anas, elevated to the Prophet: "Whoever prays Fajr in congregation, then sits remembering Allah until the sun rises, then prays two rak'ahs, will have a reward like that of a Hajj and an 'Umrah." This was also established by the action of the Prophet, peace be upon him, without mentioning a prayer after sunrise or any specific virtue for it; he used to sit in his prayer place after the Fajr prayer until the sun rose.