Is it permissible for a worshipper to move forward to the first row if there is a space in it, and there is a person directly behind him who has not yet moved forward, in emulation of the saying of the Messenger Muhammad, peace and blessings be upon him: "If you knew what was in the first row, you would fight over it with swords"?

The aforementioned hadith (definition) was not narrated with the exact wording provided, but rather with a different wording in the Two Sahihs (Bukhari and Muslim). It indicates the virtue of the adhan (definition), the first row, and hastening to prayer. The Prophet, peace and blessings be upon him, commanded the completion of the front rows. So, if people leave a gap in the row ahead, whoever sees it should fill it, and they will be rewarded for that. It is permissible to step over people's shoulders to fill a gap in the row, especially on Friday, because those who left the gap are the ones who were negligent.