Does every line have to be filled before starting another?

In the name of Allah, the most Beneficent, the most Merciful.

Answer

In a congregational prayer, if there is room in a row at the front, then to occupy a position on a row behind is disliked.  (Maraqi Falah p.132)

The Prophet of Allah Sallallahu Alahi Wasalam said, “Allah and his Angels invoke blessings on those who arrange the rows in a compact form and he who fills some space in the rows, Allah elevates him a degree on that account”.  (Sunan Ibn Majah p.70 v.1)

Only Allah Knows Best

Mohammed Tosir Miah

Darul Ifta Birmingham