I found an answer to the question here: Reduce the space between a quotation and a title. But for some reason the result is highly dependent on the code formatting and hence error prone as shown by this example:
\documentclass{article}
\usepackage{setspace}
\doublespacing
\usepackage{etoolbox}
\BeforeBeginEnvironment{quotation}{\begin{singlespace*}}
\AfterEndEnvironment{quotation}{\end{singlespace*}}
\begin{document}
double double double double double double double double double double double double double double double double double double double double double double double
\begin{quotation}
quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote
\end{quotation}
single single single single single single single single single single single single single single single single single single single single single single single single
\begin{quotation}
quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote quote
\end{quotation}
\end{document}
The "double" paragraph renders different in spacing from the "single" paragraph (the former double spaced as expected but the latter single spaced). Is this an error in the etoolbox or am I making a mistake?

\BeforeBeginEnvironment{quotation}{\par\begin{singlespace*}}– Gonzalo Medina Jun 26 '15 at 14:30