(strong and able)- means being able to do it - Surat Aal-Imraan Q. 3:97- "And Hajj (pilgrimage to Makkah) to the House (Ka‘bah) is a duly that mankind owes to Allaah. those who can afford the expenses (for one's conveyance. provision and residence)" This includes being able both physically and financially. What is meant by being physically can bear the hardship of travelling to the sacred House of Allaah. Being financially able means that one has enough funds to get to the sacred House of Allaah and back again.