What is the ruling about the one who tries to get to the first row (for prayer), tapping people on the shoulders and asking them to make way for him?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

Whoever enters the Masjid and finds the people already praying, and he sees a gap in one of the front rows, he is allowed to squeeze through the rows to reach that gap.

The basis for this is that the Prophet, sallallaahu ‘alayhi wa sallam, went to Banu ‘Aamir ibn ‘Awf to make peace between them and the time for prayer came, so the Mu’aththin went to Abu Bakr and said to him: "Should I announce the prayer and you lead?" He said: "Yes." So Abu Bakr led the prayer. The Prophet, sallallaahu ‘alayhi wa sallam, then came while the people were already praying, so he passed through the rows until he stood in the first row…" [Al-Bukhari]

If this was the case for those who are praying, then the one who passed by those who are sitting before the prayer or listening to a lecture has more right to do so. If he needs to notify the people by patting them on their shoulders, he may. It is then expected that they make way for him, due to the Hadeeth: "Be soft in the hands of your brothers." [Ahmad and Abu Daawood]

During the Khutbah (sermon) of Jumu‘ah it is apparently not permitted to do this based on the prohibition of stepping over others to get to the first row on that day, as this falls under the meaning of Laghw (making an idle action), since doing so would cause an effect similar to that of moving pebbles, and the Prophet, sallallaahu ‘alayhi wa sallam, said: "Whoever touches the pebbles has surely engaged in an idle action." [Muslim]