Surah An-Naba 78:39

ذَٰلِكَ ٱلْيَوْمُ ٱلْحَقُّ ۖ فَمَن شَآءَ ٱتَّخَذَ إِلَىٰ رَبِّهِۦ مَـَٔابًا

That is the True [i.e., certain] Day; so he who wills may take to his Lord a [way of] return.

Translation: Saheeh International

Tafsir

That is the True Day whose coming to pass is definite namely the Day of Resurrection. So whoever wishes to let him seek resort with his Lord a return to Him that is to say let him return to God by being obedient to Him so that he may be secure from chastisement in it.

Excerpt from Tafsir al-Jalalayn, commentary on 78:39, via Quran.com. The reader has the full commentary and 9 more tafsirs.