Harun Mowla Al-i-Abi Ja'da narrated that Imam Sadiq (a.s) said
“Do your best when writing “In the name of God, Most Gracious, Most Merciful” in terms of the handwriting.”
عن هارون مولى آل أبي جعدة قال
قال أبو عبد الله (عليه السلام): اكتب " بسم الله الرحمان الرحيم " من أجود كتابتك، ولا تمد الباء حتى ترفع السين.
Similar narrations
Al-Kāfi #2331“Abu ‘Abd Allah (a.s.) has said, ‘Write “(I begin) in the name of Allah, the Beneficent, the Merciful,” with the best of your handwriting....