How did the oaths of the Prophet (ﷺ) use to be?
حَدَّثَنَا يَحْيَى بْنُ سُلَيْمَانَ، قَالَ حَدَّثَنِي ابْنُ وَهْبٍ، قَالَ أَخْبَرَنِي حَيْوَةُ، قَالَ حَدَّثَنِي أَبُو عَقِيلٍ، زُهْرَةُ بْنُ مَعْبَدٍ أَنَّهُ سَمِعَ جَدَّهُ عَبْدَ اللَّهِ بْنَ هِشَامٍ، قَالَ كُنَّا مَعَ النَّبِيِّ صلى الله عليه وسلم وَهْوَ آخِذٌ بِيَدِ عُمَرَ بْنِ الْخَطَّابِ فَقَالَ لَهُ عُمَرُ يَا رَسُولَ اللَّهِ لأَنْتَ أَحَبُّ إِلَىَّ مِنْ كُلِّ شَىْءٍ إِلاَّ مِنْ نَفْسِي. فَقَالَ النَّبِيُّ صلى الله عليه وسلم " لاَ وَالَّذِي نَفْسِي بِيَدِهِ حَتَّى أَكُونَ أَحَبَّ إِلَيْكَ مِنْ نَفْسِكَ ". فَقَالَ لَهُ عُمَرُ فَإِنَّهُ الآنَ وَاللَّهِ لأَنْتَ أَحَبُّ إِلَىَّ مِنْ نَفْسِي. فَقَالَ النَّبِيُّ صلى الله عليه وسلم " الآنَ يَا عُمَرُ ".
Narrated `Abdullah bin Hisham: We were with the Prophet (ﷺ) and he was holding the hand of `Umar bin Al-Khattab. `Umar said to Him, "O Allah's Messenger! You are dearer to me than everything except my own self." The Prophet (ﷺ) said, "No, by Him in Whose Hand my soul is, (you will not have complete faith) till I am dearer to you than your own self." Then `Umar said to him, "However, now, by Allah, you are dearer to me than my own self." The Prophet (ﷺ) said, "Now, O `Umar, (now you are a believer).