What is meant by the command to "complete" Hajj and Umrah?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It means performing Hajj and Umrah separately, by doing ʿUmrah outside the months of Hajj. [ʿUmar ibn al-Khaṭṭāb, al-Ḥasan, ʿAṭāʾ]
2. It means that a person should enter the state of ihram from his home. [ʿAlī ibn Abī Ṭālib, Ṭāwūs, Ibn Jubayr]
3. It means that once one has begun either Hajj or ʿUmrah, one should not cut it short. [Ibn ʿAbbās]
4. It means doing what Allah has commanded within them. [Mujāhid]