A lot of people like to point to Palestinians and organizations saying "From the River (Jordan) to the (Red) Sea" as "evidence" of this.
Most of those people are unaware that Palestinians and those organizations directly took that saying from Likud, the hard right political party currently in power in Israel - the saying was a literal election campaign of Likud in the 1970s.
I don’t think anyone uses a saying to back claims over land.
In any case, your comment seems to suggest that Palestinians /could not/ have come up with this phrase, and had to resort to stealing the occupier’s, which is wildly misleading.
In any case, the origin of the phrase is ascertain.
This is pretty apologist. The PLO started using it while referring to Likud, so it was their version of taking it back, in the 1980s.
I'm sure they could have come up with it themselves had they wished.
But whitewashing it as just a saying on Israel's part, but a threat on Palestine's... given that multiple members of Likud, often in official capacities, openly espouse and encourage exactly that, taking more land from Palestine.
Most of those people are unaware that Palestinians and those organizations directly took that saying from Likud, the hard right political party currently in power in Israel - the saying was a literal election campaign of Likud in the 1970s.