[Machine] Omar used to swear by his father, so the Prophet ﷺ forbade him from doing so, and he said, "Whoever swears by anything other than Allah has committed shirk (associating partners with Allah)." The other person said, "So it is a form of shirk."
كَانَ عُمَرُ يَحْلِفُ وَأَبِي فَنَهَاهُ النَّبِيُّ ﷺ فَقَالَ «مَنْ حَلَفَ بِشَيْءٍ مِنْ دُونِ اللَّهِ فَقَدْ أَشْرَكَ» وَقَالَ الْآخَرُ «فَهُوَ شِرْكٌ»