It is obligatory to perform Hajj

Narrated 'Abdullah bin Abbas :

Al-Fadl (his brother) was riding behind Allah's Apostle and a woman from the tribe of Khath'am came and Al-Fadl started looking at her and she started looking at him. The Prophet turned Al-Fadl's face to the other side. The woman said, "O Allah's Apostle! The obligation of Hajj enjoined by Allah on His devotees has become due on my father and he is old and weak, and he cannot sit firm on the Mount;
may I perform Hajj on his behalf?" The Prophet replied, "Yes, you may." That happened during the Hajj-al-Wida (of the Prophet ).

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكٌ، عَنِ ابْنِ شِهَابٍ، عَنْ سُلَيْمَانَ بْنِ يَسَارٍ، عَنْ عَبْدِ اللَّهِ بْنِ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ كَانَ الْفَضْلُ رَدِيفَ رَسُولِ اللَّهِ ﷺ فَجَاءَتِ امْرَأَةٌ مِنْ خَثْعَمَ، فَجَعَلَ الْفَضْلُ يَنْظُرُ إِلَيْهَا وَتَنْظُرُ إِلَيْهِ، وَجَعَلَ النَّبِيُّ ﷺ يَصْرِفُ وَجْهَ الْفَضْلِ إِلَى الشِّقِّ الآخَرِ فَقَالَتْ يَا رَسُولَ اللَّهِ إِنَّ فَرِيضَةَ اللَّهِ عَلَى عِبَادِهِ فِي الْحَجِّ أَدْرَكَتْ أَبِي شَيْخًا كَبِيرًا، لاَ يَثْبُتُ عَلَى الرَّاحِلَةِ، أَفَأَحُجُّ عَنْهُ قَالَ " نَعَمْ ". وَذَلِكَ فِي حَجَّةِ الْوَدَاعِ.