Sunan Ibn Majah, The Book On The Mosques And The Congregations
Book 4, Hadith 64
Narrated 'It was narrated from 'Umar bin Khattab that:
The Prophet used to say: "Whoever performs prayer in congregation at the mosque for forty nights, never missing the first Rak'ah of the 'Isha' prayer, Allah will thereby decree for him salvation from the Fire." (Da'if)
Book 4, Hadith 64
Narrated 'It was narrated from 'Umar bin Khattab that:
The Prophet used to say: "Whoever performs prayer in congregation at the mosque for forty nights, never missing the first Rak'ah of the 'Isha' prayer, Allah will thereby decree for him salvation from the Fire." (Da'if)