"I had two times when I would enter upon the Messenger of Allah ﷺ, one at night and one during the day. When I entered at night he would clear his throat (to tell me to come in)." (Using translation from Nasāʾī 1212)  

قَالَ عَلِيٌّ كَانَ لِي مِنَ النَّبِيِّ ﷺ مَدْخَلَانِ مَدْخَلٌ بِاللَّيْلِ وَمَدْخَلٌ بِالنَّهَارِ فَكُنْتُ إِذَا دَخَلْتُ بِاللَّيْلِ تَنَحْنَحَ لِي  

"Ali said to me: 'I was so close to the Messenger of Allah ﷺ, closer than anyone else. I used to come to him at the end of every night, before dawn, and say: "As-salamu 'alayka ya Nabiyy Allah (Peace be upon you, O Prophet of Allah)." If he cleared his throat I would go back to my family, otherwise I would enter upon him.'" (Using translation from Nasāʾī 1213)  

قَالَ عَلِيٌّ كَانَتْ لِي مَنْزِلَةٌ مِنْ رَسُولِ اللهِ ﷺ لَمْ تَكُنْ لِأَحَدٍ مِنَ الْخَلَائِقِ فَكُنْتُ آتِيهِ كُلَّ سَحَرٍ فَأَقُولُ السَّلَامُ عَلَيْكَ يَا نَبِيِّ اللهِ فَإِنْ تَنَحْنَحَ انْصَرَفْتُ إِلَى أَهْلِي وَإِلَّا دَخَلْتُ عَلَيْهِ