Is it forbidden to rely on toes instead of heels to straighten rows? How is this wrong to be denounced? Is denouncing it in one's heart sufficient when unable to change it?

A group of scholars holds the view that straightening the rows is obligatory, citing the hadith (definition) of Nu'man ibn Bashir: "You must straighten your rows, or Allah will cause your faces to differ." Straightening is achieved by aligning the shoulders and ankles, not the fingertips. Aligning the ankles is considered valid because they are level with the body's vertical axis. There is no sin on one who straightens the rows by aligning the fingertips if they believe this achieves the required straightening, although the majority of scholars consider straightening the rows to be recommended. It is good to respectfully and wisely inform the Imam of these hadiths.