Possible meanings are 1) “Know this” as a command, to pay attention to what I am about to write or 2) “You know this” as a statement, that I am about to remind you of something that you already know.
These sayings are idioms that mean people should first listen intently, and then consider carefully what they say. Here “slow to speak” does not mean speaking slowly. (See: rc://en/ta/man/translate/figs-idiom)
“not get angry quickly”
When a person is always angry, he cannot do God’s work, which is righteous.
Sin and evil are spoken of here as if they were clothing that could be taken off. AT: “stop doing all filthy sins and stop doing abundant amounts of evil” (See: rc://en/ta/man/translate/figs-metaphor)
Here the expressions “sinful filth” and “evil” share similar meanings. James uses them to emphasize how bad sin is. AT: “stop doing every kind of sinful behavior” (See: rc://en/ta/man/translate/figs-doublet)
Here “filth,” that is, dirt, stands for sin and evil. (See: rc://en/ta/man/translate/figs-metaphor)
“Without pride” or “Without arrogance”
The expression “implant” means to place one thing inside of another. Here God’s word is spoken of as if it were a plant made to grow inside believers. AT: “obey the message God has spoken to you” (See: rc://en/ta/man/translate/figs-metaphor)
Here “word,” is a synecdoche for the message of salvation that God speaks to believers. When they believe it, God saves them. (See: rc://en/ta/man/translate/figs-synecdoche)
What a person is saved from can be made explicit. AT: “save you from God’s judgment” (See: rc://en/ta/man/translate/figs-explicit)
Here the word “souls” refers to persons.AT: “yourselves” (See: rc://en/ta/man/translate/figs-synecdoche)