Musnad Ahmad 380
It was narrated that Hisham said:
My father told me that ‘Umar bin al-Khattab (رضي الله عنه) said to the [Black] Stone; You are only a stone; were it not that I saw the Messenger of Allah (ﷺ) kiss you, I would not have kissed you. Then he kissed it.
حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، عَنْ هِشَامٍ، قَالَ أَخْبَرَنِي أَبِي أَنَّ عُمَرَ، رَضِيَ اللَّهُ عَنْهُ قَالَ لِلْحَجَرِ إِنَّمَا أَنْتَ حَجَرٌ وَلَوْلَا أَنِّي رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُقَبِّلُكَ مَا قَبَّلْتُكَ ثُمَّ قَبَّلَهُ‏.‏