Ask, seek and knock are three different senses being considered here.

Asking is verbal, we use our mouths to petition God for our needs and desires.

Seeking, uses the mind, it is setting priorities and focusing on the heart of God.

To knock involves a physical movement, we take action. 

Let's keep on asking and we will receive, keep on seeking His face and we will find His loving presence, and we keep on knocking until the door is open. This is what prayer is all about.

ask seek knock