What is the authenticity of the Hadith: "Allah Almighty said: 'Indeed My houses on Earth are the mosques, and My visitors therein are those who frequent them. So, blessed is a servant who purifies himself in his home then visits Me in My House, for it is incumbent upon the host to honor his guest'"?

The aforementioned hadith (definition), with this wording, is weak, as mentioned by Az-Zayla'i and Al-'Iraqi. However, there is something that supports it: "Whoever performs ablution (wudu') in his house, and performs it well, then comes to the mosque, he is a visitor of Allah Almighty, and it is incumbent upon the host to honor his visitor." This was narrated by Al-Tabarani, and its chain of narration was authenticated by Al-Haythami and Al-Suyuti, and graded as hasan (definition) (good) by Al-Albani. Likewise, Al-Bayhaqi narrated a similar narration, mawquf (stopped at the Companions), with an authentic chain of narration.