Assalaamu alaykum. I have a question regarding the difference between neglecting and forgetting the prayer. If there are 30 minutes left for 'Asr and I wait with the intention of praying in about 15 minutes, and then, while I am eating, I forget about 'Asr and the sun goes down. Does this fall under neglect or forgetting, because I forgot at the end? May Allah reward you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallAllaahu ʻalayhi wa sallam, is His slave and Messenger. 

It was narrated on the authority of Anas that the Prophet, sallallaahu ʻalayhi wa sallam, said, “If any one of you forgets a prayer or sleeps and misses it, then let him pray it whenever he remembers it.” [Al-Bukhari and Muslim] Another version reads, “There is no expiation for it except for that (i.e. praying it whenever he remembers it).”

The Islamic sharee'ah has set specific times for the obligatory prayers; Allaah, The Exalted, says (what means): {Indeed, prayer has been decreed upon the believers a decree of specified times.} [Quran 4:103]

Many scholars held that there are two times for performing the ʻAsr prayer; a preferred time and a time of necessity. Please, refer to fatwa 84538.  They held different views, though, regarding identifying the exact beginning and end of the preferred time (i.e. the time when it is permissible to perform the prayer at any point within it and it is not disliked). It was said that it lasts from the beginning of the time of ʻAsr until the sun begins to turn yellow; it was also said that the preferred time continues until the shadow of an object is twice the height of the object. As for the time of necessity, it refers to the maximum time after which a person is prohibited to delay the prayer for no valid excuse. Ibn Qudaamah wrote:

“There are different views reported on the authority of Ahmad regarding the end of the preferred time (of the ʻAsr prayer); it has been narrated on his authority that it lasts until the length of the shadow is twice the length of the object itself. This view was adopted by Maalik, Ath-Thawri, and Ash-Shaafiʻi, and it is evidenced by the hadeeth reported by Ibn 'Abbaas and Jaabir, which reads, ‘...the time of prayer is in between these two times (the first is when the length of the shadow of an object is equal to the length of the object and the second is when the length of an shadow is twice the length of the object).’ It was also reported on the authority of Ahmad that the preferred time of the ʻAsr prayer lasts until the sun turns yellow. This is the most correct view reported on his (Imaam Ahmad's) authority, as narrated by a group of his students, including Al-Athram, who said, 'I heard someone ask him (Imaam Ahmad) about the time of the ʻAsr prayer, and he replied, 'It is up to the time when the sun changes (turns yellow).' He was further asked, 'Do you not hold that the preferred time lasts until the length of the shadow is equal to or twice the length of the object?' He answered, 'No; I believe that it lasts more than that.' This view was adopted by Abu Thawr, Abu Yoosuf, Muhammad, and Al-Awzaaʻi as evidenced by the hadeeth narrated on the authority of ʻAbdullaah ibn ʻAmr that states that the Prophet, sallallaahu ʻalayhi wa sallam, said, 'The time for ʻAsr is as long as the sun has not turned yellow (pale).'  [Muslim] It is impermissible to delay the ʻAsr after the preferred time for no valid excuse.”

If you mean that you have delayed the ʻAsr prayer until there was only half an hour to the end of the preferred time, then you should know that forgetfulness in this case waives the sin, because if you deliberately delay a prayer until there is only enough time to perform it (before its fixed time expires), you bear no sin; however, you would miss the rewards of performing the prayer at the beginning of its due time. If you forget performing the prayer during the preferred time during which delaying its performance is allowable, then this falls under forgetfulness and not negligence.

On the other hand, if you mean that you delayed the ʻAsr prayer until the last half hour of the necessity time ... i.e. half an hour was left to sunset, then you should know that it is impermissible for you to delay ʻAsr prayer until this time without a valid excuse. If one delays the ʻAsr prayer until that time due to a valid excuse, then as soon as that excuse ceases to exist, he is obliged to hasten to perform the delayed prayer; if he does not do so and delays it for no valid excuse, then he bears a sin for that, and forgetting to perform it in this case falls under the category of negligence.

Some scholars held that the person bears no sin for delaying the ʻAsr prayer until the last half hour before sunset; however, it is not preferable as long as it is performed before the sun turns yellow, and it is disliked if it is performed after the sun becomes yellow. An-Nawawi wrote:

“Al-Qaadhi Husayn, As-Saydalaani, Imaam Al-Haramayn, Ar-Rooyaani, and others stated that the ʻAsr prayer has five times: 1. The most virtuous time, 2. The preferred time, 3. The allowable time in which there is no dislike, 4. The allowable time that contains dislike, 5. And the time that is due to an excuse or necessity. The most virtuous time is at the beginning of the permissible time until the shadow of an object is equal to one and a half times its length. The preferred time is until the shadow of an object is twice the length of the object. The permissible time without dislike is from the time that the sun becomes yellow. The permissible time with dislike is from the time the sun becomes yellow until the setting of the sun. The time of excuse or necessity begins at the time of the Thuhr (noon) prayer for one who is to combine the Thuhr and ʻAsr prayers due to traveling or (heavy) rain.” [Sharh Al-Muhaththab]

Based on this scholarly view, there is no harm in delaying the performance of the ʻAsr prayer to that time and you bear no sin for that; however, you have missed the rewards for performing it in the preferred time. In any case, this still counts as negligence in performing the prayer on time on your part.

Allaah knows best.