Sunan an-Nasa'i 4186

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا حَاتِمُ بْنُ إِسْمَاعِيلَ، عَنْ يَزِيدَ بْنِ أَبِي عُبَيْدٍ، عَنْ سَلَمَةَ بْنِ الأَكْوَعِ، أَنَّهُ دَخَلَ عَلَى الْحَجَّاجِ فَقَالَ يَا ابْنَ الأَكْوَعِ ارْتَدَدْتَ عَلَى عَقِبَيْكَ وَذَكَرَ كَلِمَةً مَعْنَاهَا وَبَدَوْتَ ‏.‏ قَالَ لاَ وَلَكِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم أَذِنَ لِي فِي الْبُدُوِّ ‏.‏

It was narrated from Salamah bin Al-Akwa ' that he entered upon Al-Hajjaj who said:O son of Al-Akwa, you have turned on your heels (i.e., deserted Islam) by staying in the desert with the Bedouins." He said: "No; the Messenger of Allah gave me permission to stay in the desert with the Bedouins

Reference

Sunan an-Nasa'i 4186

In-book

Book 39, Hadith 38