"I heard Jabir bin Samurah being asked about the gray hairs of the Prophet [SAW]. He said: 'If he put oil on his head they could not be seen, but if he did not put oil on his head, they could be seen.'"  

عَنْ شَيْبِ رَسُولِ اللَّهِ ﷺ قَالَ كَانَ إِذَا ادُّهِنَ رَأْسُهُ لَمْ يُرَ مِنْهُ وَإِذَا لَمْ يُدَّهَنْ رُئِيَ مِنْهُ  

[Machine] From the white hair of the Prophet ﷺ , he said, "There were hairs on his head that, when he would apply oil to his head, they would not become visible, and when he would not apply oil, they would become visible."  

عَنْ شَيْبِ النَّبِيِّ ﷺ قَالَ كَانَ فِي رَأْسِهِ شَعَرَاتٌ إِذَا دَهَنَ رَأْسَهُ لَمْ تَتَبَيَّنَّ وَإِذَا لَمْ يَدْهُنْهُ تَبَيَّنَّ  

When he oiled his head nothing was seen (as a mark of old age) and when he did not apply oil something (of the old age) became visible. (Using translation from Muslim 2344a)  

عَنْ شَيْبِ النَّبِيِّ ﷺ قَالَ «كَانَ إِذَا دَهَنَ رَأْسَهُ لَمْ يُرَ مِنْهُ وَإِذَا لَمْ يَدَّهِنْ رُئِيَ مِنْهُ»