Allah says: " 31:16 "O my son!If it be (anything) equal to the weight of a grain of mustard seed, and though it be in a rock, or in the heavens or on the earth, Allah will bring it forth."

To whom speaks Allah there? I tried to get an answer by reading the tafsir of Ibn Kathir, but there is nothing written about that.

Surah 31. Luqman

31:16

"O my son!" (said Luqman), "If there be (but) the weight of a mustard-seed and it were (hidden) in a rock, or (anywhere) in the heavens or on earth, Allah will bring it forth: for Allah understands the finest mysteries, (and) is well-acquainted (with them).

Name

The Surah has been named Luqman after Luqman the Sage, whose admonitions to his son have been related in vv. 12-19 of this Surah.


http://www.islamicity.com/quran/maududi/mau31.html

Barakallahu Feek!