Tafsir of Al-Ahqaf 46:13

{Indeed, those who say, "Our Lord is Allah," and then remain on a righteous course...} that is, those who have combined the oneness of God—which is the essence of knowledge—with steadfastness in religion—which is the culmination of action. The particle "then" (thumma) here denotes a delay in rank (tarakhi rutbi); for action is secondary in rank to the oneness of God, and the scholars have established that it is not considered valid without it.

{...no fear will there be concerning them...} that is, no hateful thing shall befall them.

{...nor will they grieve...} that is, over the loss of any beloved thing. The intent is the continuity of this negation. The particle "fa" (fala) is used because the noun [in the phrase "those who"] implies the meaning of a condition, while retaining the meaning of an initialization; therefore, it does not enter into the predicate of layta (would that), la’alla (perhaps), or ka’anna (as if), even if their subjects are relative pronouns (mawsulat). A parallel to this verse has preceded in Surah as-Sajdah, and we have mentioned therein what we have mentioned in its exegesis, so let it be consulted.