Sunan an-Nasa'i, Hadith 5521 ⓘ
It was narrated that Anas bin Malik said: "The Messenger of Allah [SAW] said: 'Whoever asks Allah for Paradise three times, Paradise will say: 'O Allah, admit him to Paradise.' And whoever seeks protection from Hell three times, Hell will say: 'O Allah, protect him from the Fire.'"
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا أَبُو الأَحْوَصِ، عَنْ أَبِي إِسْحَاقَ، عَنْ بُرَيْدِ بْنِ أَبِي مَرْيَمَ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ سَأَلَ اللَّهَ الْجَنَّةَ ثَلاَثَ مَرَّاتٍ قَالَتِ الْجَنَّةُ اللَّهُمَّ أَدْخِلْهُ الْجَنَّةَ وَمَنِ اسْتَجَارَ مِنَ النَّارِ ثَلاَثَ مَرَّاتٍ قَالَتِ النَّارُ اللَّهُمَّ أَجِرْهُ مِنَ النَّارِ " .
also referenced under: Book 50, Hadith 94 (In-Book) & Volume 6, Book 50, Hadith 5523 (DarusSalam)