The "speck" (Gr. karphos) could be a speck of any foreign matter. The "log" or "plank" (Gr. dokos) refers to a large piece of wood. Jesus again used hyperbole to stress the folly of criticizing someone else. This act reveals a much greater problem in the critic"s life, namely, a censorious spirit. [source][source][source]
Such a person is a hypocrite and his actions carry him away. He does not deceive others as much as he deceives himself. Other people may realize that his criticism is unjustifiable, but he does not. A proper attitude is important in judging oneself and other people ( 1 Corinthians 11:31; Galatians 6:1). Censorious critics are not helpful. That is what Jesus warned against here (cf. Luke 6:39-42). [source][source][source]
"The disciples of the King are to be critical of self but not of their brethren. The group is to be noted for their bond of unity, which is indicated by a lack of criticism. This is fitting, since the kingdom is characterized by peace. ( Isaiah 9:7)." [1][source]