For this reason al-Ḥāfiẓ said in Fatḥ al-Bārī, after quoting the additional wording I cited from the first report narrated by Anas:

“This explicit wording shows that the described action took place in the time of the Prophet ﷺ, and on that basis it serves as decisive evidence for what is meant by establishing and straightening the row.”

It is regrettable that this sunnah of straightening the rows has been treated lightly by Muslims—indeed, it has been lost except among a few. I have not seen it practised by any group except the people of ḥadith. I observed them in Mecca in the year 1368 AH, keen to adhere to it just as they uphold the other practices of the Chosen Prophet ﷺ. As for the followers of the four schools—none of them, not even the Ḥanbalīs, are exempt—this sunnah has become a forgotten relic among them. Rather, they have persisted in abandoning and disregarding it because most positions in their madhhabs state that the sunnah when standing is to leave a gap between the feet roughly four fingers wide, and that anything wider is disliked, as set out in al-Fiqh ʿalā al-Madhāhib al-Arbaʿah (1/207). That measurement, however, has no basis in the Sunnah; it is a mere opinion. Even if it were sound, it would have to be limited to the imam or to a person praying alone so that it would not conflict with this authentic sunnah, as the principles of legal methodology require.

In short, I urge the Muslims—especially the imams of the mosques—who are keen to follow the Prophet ﷺ and earn the virtue of reviving his sunnah, to act upon this practice, safeguard it, and invite the people to it until they all adopt it together. By doing so they will be spared the warning: “or else Allah will cause your hearts to differ.”