Is it permissible to roll up one’s trousers from the outside during prayer to avoid letting them hang below the ankles (isbal), or is it better to leave them hanging, or must they be rolled up from the inside, and does the same ruling apply to shirts?

Trailing one's garment (Isbal) is absolutely forbidden. Whoever prays with his garment trailing is sinful, due to the Prophet's (peace be upon him) saying: "Whatever is below the ankles of the izar (lower garment) is in the Fire."

The Prophet (peace be upon him) commanded anyone who was praying with his garment trailing to perform ablution (wudu'), and said: "Indeed, Allah Almighty does not accept the prayer of a man who trails his izar." The reason for this is that trailing is a sin, and ablution extinguishes the fire of sin.

As for the Prophet's (peace be upon him) prohibition of tucking up garments and hair during prayer, its meaning is gathering and compressing them. This is a prohibition of disliking (karahah tanzih) according to the majority of scholars. So, whoever prays with his garment tucked up or his hair braided has done wrong, but his prayer is valid.