Surah Ash-Sharh 94:3

ٱلَّذِىٓ أَنقَضَ ظَهْرَكَ

Which had weighed upon your back

Translation: Saheeh International

Tafsir

that which weighed down your back? — this is similar to where God says that God may forgive you what is past of your sin Q. 482.

Excerpt from Tafsir al-Jalalayn, commentary on 94:3, via Quran.com. The reader has the full commentary and 9 more tafsirs.