What is the ruling on someone who points at his colleague with his hand when saying "I seek refuge in Allah from the accursed Satan," intending that the colleague is the Satan, and is this considered an act of disbelief (kufr)?

What has been mentioned is not considered disbelief (kufr). Indeed, there are devils among humans, and it is prescribed to seek refuge from them. A person's saying to another, "O devil" or "O disbeliever," is not considered disbelief. The hadiths reported regarding this are interpreted as referring to minor disbelief (kufr asghar). Scholars have cited the hadith: "Cursing a believer is like killing him, and whoever accuses a believer of disbelief is like killing him." And killing is not disbelief. Ibn Taymiyyah clarified that the hadith refers to the one being addressed as "brother" at the time of the statement; if either of them were to totally abandon Islam, he would no longer be his brother. Ibn Qudamah indicated that these hadiths are for warning and resemblance to disbelievers, not for literal interpretation.