Hadith comprehension

What is the role of كَثِيرًا in اسْتِغْفَارًا كَثِيرًا?

Speaking the Truth, Striving in Allah's Path, and Understanding the Religion (Hadith 51-56)

• Adjective modifying اسْتِغْفَارًا
• Negative particle
• Imperative verb
• Separate subject