how to add word in the line?

Question

I want to add the word in the line using the bellow code, now the picture is :

I want to add the word "p1" in the line between "a" and "b" which looks like:

I try to modify the code to \path [line] (a) -- (b){p1}; but there is an error.

\usetikzlibrary{shapes,arrows,positioning}
   \usepackage{wrapfig}
  \usepackage{graphicx}
   \resizebox{.4\textwidth}{!}{\begin{tikzpicture}[
block/.style = {circle, draw,align=center,text width = 0.1cm, inner sep = 0.1cm},
    line/.style = {draw,thick, -latex'},
    node distance=0.9cm and 0.4cm
    ]

    % Place nodes
    \node [block] (a) {a};
    \node [block, below left of=a,xshift=-1.0cm, yshift=-0.3cm] (b) {b};
    \node [block, below right of=a,xshift=1.0cm, yshift=-0.3cm] (c) {c};
% Draw edges
\path [line] (a) -- (b);
\path [line] (a) -- (c);

\end{tikzpicture}}

Answer 1

\path [line] (a) -- node [sloped] {p1} (b) 

it works