What is the meaning of the saying of Al-Farooq, "For this the narration occurred," when he reached the verse: "A soul knows what it has put forth"?

What Umar ibn al-Khaṭṭāb meant by his saying, "For this the story was narrated," is that the phrase "a soul will know what it has brought forth" is the answer to the oath with which the beginning of the Surah started.

And the meaning of "علمت" (calimat) is that it will be informed of what it has brought forth.