user8751: I have played a game this morning where I reached the following position:
[fen "r1bq1rk1/1p1nppbp/p2p1np1/2pP4/2P1P3/2N1BN2/PP2BPPP/R2Q1RK1 w - - 0 1"]

I was playing with White. In this position my opponent played e5 which is a very bad move because I can take the pawn en passant and then take the d6 pawn which is unprotected.
I went on to win the game and afterwards I was talking to him and he told me that he thinks that it is an usual move and that taking on d6 is not supposed to be good. 
I checked the position with my computer and it gives White an advantage of +2 after taking the d6 pawn. I assume that he forgot his analysis and mixed different lines. 
I don't usually play the King's Indian so I'm wondering, are there any lines where Black can play e5 in a position similar to this one and then is bad to take on d6?
I'm just interested in positions which arose from the King's Indian where Black has already played c5.

user4418: In KID positions like this with pawns on c5 and d6, knight on d7 I have never seen e5 without either Re8 or Qe8 first. e5 in this position is just a blunder,

user825: ...e5 is indeed a typical move in King's Indian, but it's usually done when:

The white pawn is on d4
The white pawn is on d5 but there is something defending the d6 pawn, usually the Black queen.

I think your opponent simply confused the position and blundered.

8751: <p>I have played a game this morning where I reached the following position:</p>

<pre><code>[fen "r1bq1rk1/1p1nppbp/p2p1np1/2pP4/2P1P3/2N1BN2/PP2BPPP/R2Q1RK1 w - - 0 1"]
</code></pre>

<p>I was playing with White. In this position my opponent played e5 which is a very bad move because I can take the pawn <em>en passant</em> and then take the d6 pawn which is unprotected.</p>

<p>I went on to win the game and afterwards I was talking to him and he told me that he thinks that it is an usual move and that taking on d6 is not supposed to be good. </p>

<p>I checked the position with my computer and it gives White an advantage of +2 after taking the d6 pawn. I assume that he forgot his analysis and mixed different lines. </p>

<p>I don't usually play the King's Indian so I'm wondering, are there any lines where Black can play e5 in a position similar to this one and then is bad to take on d6?</p>

<p>I'm just interested in positions which arose from the King's Indian where Black has already played c5.</p>
 4418: <p>In KID positions like this with pawns on c5 and d6, knight on d7 I have never seen e5 without either Re8 or Qe8 first. e5 in this position is just a blunder,</p>
 825: <p>...e5 is indeed a typical move in King's Indian, but it's usually done when:</p>

<ul>
<li>The white pawn is on d4</li>
<li>The white pawn is on d5 but there is something defending the d6 pawn, usually the Black queen.</li>
</ul>

<p>I think your opponent simply confused the position and blundered.</p>
