Shaykhul Islaam Ahmad ibn Taymeeyah 728AH (May Allah have mercy on him) said,

والشيطان وسواسٌ خناسٌ ، إذا ذكر العبدُ ربَّه خنس ، فإذا غفل عن ذكره وسوس

“Shaytaan is a retreating whisperer (waswaas khannaas). If the slave remembers his Lord (Shaytaan) will retreat, and if the slave is forgetful (Shaytaan) will whisper.”

Taken from: Majmu’ al-Fataawa 4/34