Deploying artifacts to the target server with Jenkins via SSH

For this, install SSH Agent Plugin.

Add your identity to the credentials: Manage Jenkins -> Credentials -> System -> Global credentials
Kind: SSH username with private key
Scope: Global
Enter username and Enter directly Private key
Enter Passphrase if you have it and hit Create

Next, create pipeline like this:

pipeline {
    agent any
    stages {
        stage ('Deploy') {
            steps {
                sh 'echo test > artifact.txt'
                sshagent(['debian']) {
                    sh 'scp -o StrictHostKeyChecking=no artifact.txt dmitritelinov@192.168.122.138:/tmp/artifact.txt'
                }      
           }       
	}
    }
}