Some words have special treatment of ṣād and sīn because of their orthography or recitational variation. Forms such as basṭah in al-Baqarah and al-Aʿrāf require attention to the specific transmitted reading.
Do not replace ṣād with sīn—or vice versa—everywhere by mere visual analogy.
The exact occurrence and the adopted riwāyah determine how it is read.