If you have shell access then run below command:
php shell/compiler.php disable
Otherwise comment out the two define function calls in includes/config.php path
#define('COMPILER_COLLECT_PATH', dirname(__FILE__).DIRECTORY_SEPARATOR.'stat');
#define('COMPILER_INCLUDE_PATH', dirname(__FILE__).DIRECTORY_SEPARATOR.'src');
And check index.php in your magento root directory and comment out the following line if uncommented:
/**
* Compilation includes configuration file
*/
/**#$compilerConfig = ‘includes/config.php';
#if (file_exists($compilerConfig)) {
include $compilerConfig;
#} */
Hope it helps you 
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