While writing latex I sometimes have to reference an equation. I do that using reftex-reference (bound to C-c ( by default). However, I sometimes want to copy some text from the equation text I just referenced.

Ideally, I would like to position my pointer at the equation label and hit some keys to jump to that equation text, or maybe show the equation text in some temporary buffer so that I can copy text from it.

Is there such a functionality in reftex or any other package?

Reftex has this feature. It's called reftex-view-crossref. See the manual about this here. It is invoked by pressing C-c & while your pointer is on the argument of the \ref{argument}.