Source: Tafsir al-Ahlam al-Kabir (Ibn Sirin)
The gathering (on Judgment Day) in a dream indicates the ruler's soldiers or a great strife. Whoever sees himself being gathered will fall into hardship.
Source: Ta'tir al-Anam fi Ta'bir al-Manam (Al-Nabulsi)
The gathering indicates oppression and injustice. Whoever sees himself in the gathering place (Mahshar) will witness oppression.
Source: Al-Isharat fi Ilm al-Ibarat (Ibn Shahin)
The gathering is interpreted as worry and grief. Whoever sees himself gathered alone, his worry will be prolonged.