Can This Ayah Be Used to Justify Child Marriage

No, this ayah does not justify child marriage. There are several arguments against that reading.

First, the Arabic: "those who did not have their period" — اللَّائِي لَمْ يَحِضْنَ — is not "those who haven't had their period yet." The first refers to a permanent biological condition, a woman who simply never menstruates due to a medical or physiological state. The second would be a girl who has not yet reached puberty. These are completely different situations and the Arabic does not support reading this as the latter.

Second, the word نِسَاء (nisa') used in this ayah is not used for children in Arabic or in the Quran. It is used exclusively for grown women. There is no precedent in the Arabic language for using nisa' to refer to underage girls.

Third, from a historical perspective: the idea that child marriage was widespread and normal in early Islamic civilization is simply not supported by reliable historical data. It is a false assumption that has been imposed on the text.

I feel very strongly that there are entire surahs of the Quran that are supposed to set the cultural tone for how Muslims conduct their family life — and these are among the most abandoned surahs in terms of genuine engagement. I urge everyone to go through the Deeper Look series on Surah At-Talaq and related surahs carefully. This is serious — millions of families have paid the price for ignoring what Allah is actually saying in these ayat.