"If you disbelieve, then indeed Allah is free from need of you," meaning: from your worship. "And He does not approve of disbelief for His servants. And if you are grateful," meaning: if you believe, "He approves it for you."
"And no bearer of burdens will bear the burden of another," meaning: no one shall carry the sin of another. "Indeed, He is All-Knowing of that within the breasts," meaning: of what is in the chests.
Tafsir of Surah Az-Zumar from verse 8 to verse 10.