ثُمَّ بَعَثناهُم لِنَعلَمَ أَيُّ الحِزبَينِ أَحصىٰ لِما لَبِثوا أَمَدًا

Then We roused them that We might know which of the two groups better reckoned the period they had stayed.

EXEGESIS

Baʿathnā means to set into motion that which is stationary.^{‎[1]Muhit, 7/145.} Here it means that God woke them from their slumber.^{‎[2]Tabrisi, 6/698.} It is worth noting that this word is often used in the Quran to refer to the resurrection.^{‎[3]See for example 22:5, 22:7, 30:56, 16:38, 19:15, and 72:7.} Its choice here is purposeful, as it conjures for the reader the connection of the story to resurrection. This hints at what is discussed further in verse 21, that the purpose of them sleeping and being woken up was to prove to the people that God can resurrect the dead bodies. Having said that, the youths were not dead, but rather sleeping, as we mentioned earlier.

Aḥṣā (reckoned) comes from ḥaṣā meaning pebbles. It is said this is because pebbles were used for counting, like fingers.^{‎[4]Raghib, p. 240.} It means here that to count and know how many years they had slept in the cave.

Some have said that aḥṣā is the comparative/superlative form of iḥṣāʾ,^{‎[5]Such as Tabari, 15/137; Baghawi, 3/182.} which would lead to the translation ‘better reckoned’, but this is not a very eloquent usage of the phrase and that is why most scholars have understood aḥṣā as being the past tense verb, such as in the verse, Allah has kept account (aḥṣā) of it (58:6), which is the more common expression and would then translate the verse as ‘which of the two groups calculated the period they had stayed’.^{‎[6]Tabrisi, 6/696; Zamakhshari, 2/705; Razi, 21/430; Mizan, 13/249. See Muhit, 7/146-148 and Alusi, 8/204-206, for an overview of the various grammatical arguments and their proponents.}

Amad (period) is close in meaning to abad (forever), however abad is an unlimited amount of time, whereas amad is a limited amount of time the exact length of which is unknown.^{‎[7]Raghib, p. 88.}

EXPOSITION

The final portion of the story’s summary is related in this verse. The story was thus summarised in three verses in three parts: 1. A group of youths took refuge in a cave and prayed to God. 2. They were then put to sleep by Him. 3. Only to be woken up later.

As they slept for such a long time, them being woken is comparable to being resurrected.^{‎[8]Nemuneh, 12/358.} Even the expressions used in verse 19 are very similar to expressions quoted from those waking from death on the Day of Resurrection.^{‎[9]See for example 23:112-113.}

That We might know: this expression is used often in the Quran and does not mean that God was unaware of something and needs to learn it, but rather that the decree of God regarding it should become a manifest reality.^{‎[10]Mizan, 13/249; Nemuneh, 12/358; Tantawi, 8/478.} In other words, what God knows should come to pass. This was also discussed in more detail in verse 7. For more, see the commentary on verse 2:143.

While there are several possibilities for who is meant by the two groups, the most obvious one is that it should be referring to two groups amongst the People of the Cave when they disagreed amongst each other, as per the later verse, So it was that We roused them [from sleep] so that they might question one another. One of them said: ‘How long have you stayed [here]?’ They said: ‘We have stayed a day, or part of a day.’ They said: ‘Your Lord knows best how long you have stayed’ (verse 19).^{‎[11]Mizan, 13/249; Nemuneh, 12/358; Tantawi, 8/478.} The reason why they questioned each other was because they all felt that they had slept longer than they initially intended, and the length of their sleep affected their plans, as they were fugitives. They concluded: Your Lord knows best how long you have stayed, showing that they did not in fact have any idea and they were quite unaware of it. So when God declares We roused them that We might know which of the two groups better reckoned the period they had stayed, He knew that none of them could ever guess or speculate that three centuries had passed. This ties in with the main theme of the surah and the inadequacy of man’s knowledge.

In other words, one of the purposes God put them to sleep in the cave for three centuries was so that upon waking they would question each other about it, and through the events that transpired they would come to realise what had happened. This would strengthen their conviction in God and deepen their faith, which is further expounded in the next verse, and We had enhanced them in guidance.

Another possibility is that We might know has the meaning of ‘to transpire’, like in the verse, and so that Allah may know those who help Him and His apostles in [their] absence (57:25). Thus the reality was in effect unimaginable to them, and by witnessing it they increased in faith and certainty.

REVIEW OF TAFSĪR LITERATURE

There are several other possibilities with regards to what is meant by the two groups:

1. It could be referring to two groups amongst the people who found them later in the cave after they awoke. If it is, then it is not clear whether both groups were believers, or disbelievers, or one of each.^{‎[12]Tibyan, 7/13-14. This is the opinion preferred by Tabrisi, 6/698, saying their people were divided into believers and disbelievers. Although some have even suggested that the People of the Cave themselves were not all believers, but a mix of believers and disbelievers (this opinion is attributed to Mujāhid ibn Jabr, Muhit, 7/146). This is contradictory to the explicit statement of verse 13.}
2. It has also been suggested that the two groups refer to the People of the Cave and the ruler and his retinue who came after them.^{‎[13]As related by Razi, 21/430.} Or that one group is the youths in the cave and the other is the people of the city.^{‎[14]Qurtubi, 10/364.}
3. They are the Jews and the Christians, who had given the Meccans the questions to ask the Holy Prophet.^{‎[15]As related by Muhit, 7/146. See the Introduction for the background to this.}
4. It refers to God and the creation, like in the verse, is it you who know better, or Allah (2:140).^{‎[16]As related by Alusi, 8/203.}

None of the above interpretations is inherently wrong, although some of them are farfetched. Perhaps the vague expression of the two groups is used to cause the reader to ponder on the verse more.

[1] Muhit, 7/145.
[2] Tabrisi, 6/698.
[3] See for example 22:5, 22:7, 30:56, 16:38, 19:15, and 72:7.
[4] Raghib, p. 240.
[5] Such as Tabari, 15/137; Baghawi, 3/182.
[6] Tabrisi, 6/696; Zamakhshari, 2/705; Razi, 21/430; Mizan, 13/249. See Muhit, 7/146-148 and Alusi, 8/204-206, for an overview of the various grammatical arguments and their proponents.
[7] Raghib, p. 88.
[8] Nemuneh, 12/358.
[9] See for example 23:112-113.
[10] Mizan, 13/249; Nemuneh, 12/358; Tantawi, 8/478.
[11] Mizan, 13/249; Nemuneh, 12/358; Tantawi, 8/478.
[12] Tibyan, 7/13-14. This is the opinion preferred by Tabrisi, 6/698, saying their people were divided into believers and disbelievers. Although some have even suggested that the People of the Cave themselves were not all believers, but a mix of believers and disbelievers (this opinion is attributed to Mujāhid ibn Jabr, Muhit, 7/146). This is contradictory to the explicit statement of verse 13.
[13] As related by Razi, 21/430.
[14] Qurtubi, 10/364.
[15] As related by Muhit, 7/146. See the Introduction for the background to this.
[16] As related by Alusi, 8/203.