Is there sin for hastening or delaying a recommended prayer time?
Chapter on Prayer Times
Al-Mughni
Book of Prayer
Primary text
A person does not incur sin for hastening a prayer that is recommended to be delayed, nor for delaying a prayer that is recommended to be hastened, provided they intend to perform it. This allowance continues as long as the legal time for the prayer has not expired, or has not become so restricted that it cannot accommodate the entirety of the act of worship. The evidence for this is that Jibreel led the Prophet (peace be upon him) in prayer at the beginning and the end of the prescribed time, and the Prophet (peace be upon him) prayed at both extremes, stating, "The time is between these two [times]." Furthermore, since the obligation is broad (mūsa‘), it is like expiation (kaffārah), which is an obligation spread out between specific instances. This principle holds as long as the individual intends to perform the act later.
Supporting text
If one delays the prayer without the intention to perform it later, sin is incurred due to that delay coupled with the lack of firm intention. Sin is also incurred if the delay is so extensive that the remaining time is insufficient for the entire prayer, because the final rak'ah is part of the whole prayer, and it is not permissible to delay it past the prescribed time, just like the first rak'ah.