His (saw) saying, "Journey [to Allah] in the beginning of the day, the end of the day, and a portion of the latter part of the night" has the meaning of his (saw) saying in another narration, "Seek help in this by journeying [to Allah] at the beginning of the day, at the end of the day and a portion of the latter part of the night."
The meaning of this is that these three periods are times of journeying to Allah through performing actions of obedience. These are the end of the night, the beginning of the day, and the end of the day. Allah, Exalted is He, has mentioned these times in His sayings,
Remember the name of thy Lord at morn and evening, and worship Him (a portion) of the night, and glorify Him through the livelong night. [Quran, 76:25-26]
And glorify your Lord - all the while praising Him - ere the rising of the sun and ere the going down thereof. And glorify Him some hours of the night and at the two ends of the day: that you may be well pleased.[Quran, 20:130]
And glorify your Lord - all the while praising Him - before the rising of the sun and before its setting; and in the night-time glorify Him, and after the (prescribed) prostrations. [Quran, 50:39-40]
Allah, Most High, mentions the remembrance of Him at the two ends of the day in numerous places in His Book such as,
O you who believe! Remember Allah with much remembrance and glorify Him morning and evening. [Quran, 33:41-42]
And ask forgiveness for your sin, and glorify your Lord - all the while praising Him - at the fall of night and in the early hours. [Quran, 40:55]
Repel not those who call upon their Lord at morn and evening, seeking His face. [Quran, 6:52]
He said concerning the remembrance of Zakariyyah (as)
...and signified to them: Glorify (your Lord) at morning and fall of night. [Quran, 19:11]
...and glorify (Him) at the fall of night and in the early hours. [Quran, 3:41]
Out of these three times there are two which are at the beginning of the day and the end of the day. At these two times one finds both obligatory and optional actions to do. The obligatory actions are the prayers of Fajr and Asr and these two are the best prayers of the five daily prayers. These are the prayers prayed "at the two cool periods," and whoever preserves these two prayers shall enter Paradise. [Bukhari & Muslim] It is said about both these prayers that they are the "Middle Prayer." As for the optional deed then it is to remember Allah after the Fajr prayer until the sun rises and after Asr until the sun sets, there are many texts concerning the excellence of this. Likewise there are many texts concerning the remembrances to be said in the morning and evening and concerning the excellence of one who remembers Allah when awaking and when sleeping.
Ibn Umar reports that the Messenger of Allah (saw) said, "Son of Adam, remember me for an hour in the beginning of the day and an hour at the end and I will forgive you your sins committed between them save any major sins for which you must repent." [Abu Nuaym]
The Salaf would place greater emphasis on the end of the day than the beginning. Ibn al-Mubarak said, 'It has reached us that the one who remembers Allah at the end of the day will be recorded as having performed remembrance throughout the day.' Abu'l-Jald said, 'It has reached us that Allah, Exaited is He, descends to the lowest heaven during the eve of every day and looks at the deeds of the children of Adam.'
One of the Salaf saw Abu Jafar al-Qari in a dream saying to him, 'Tell Abu Hazim - al-Araj i.e. - the ascetic and highly perspicuous person - that Allah and His Angels look to your gathering in the evenings.' [Ibn al-Jawzi] It seems clear that Abu Hazim used to narrate stories to people at the end of the day.
A Hadith mentions, "Remembrance after Fajr is more beloved than freeing four slaves and remembrance after Asr is better than freeing eight slaves." [Ahmad]
The end of the day of Jumuah is better than its beginning due to its containing an hour wherein the supplication is answered. [Bukhari & Muslim] The end of the Day of Arafah is better than the beginning because the end of the day is the time for standing. The end of the night is better than the beginning of the night as was stated by the Salaf and they adduced the hadith of the Descent as proof.
All of these facts strengthen the opinion of those who say that Asr is the "Middle Prayer."
The third period is the duljah:journeying in the last part of the night. The meaning here is performing deeds at the end of the night which is the time for asking forgiveness.
Allah, Exalted is He says,
And those who ask forgiveness in the early hours of the morning. [Quran, 3:17]
And ere the dawning of each day would seek forgiveness. [Quran, 51:18]
The period referred to in these verses is the last part of the time of the Descent in which Allah fulfils the needs of those asking and grants forgiveness to the penitent. The middle of the night is reserved for the lovers who wish to spend time in intimacy with their Beloved and the end of the night is reserved for the sinners to seek forgiveness for their sins. Whoever is unable to join the striving of the lovers in the depth of the night should at least join the penitent at the end of the night.
Some narrations mention that the Throne quivers during the last part of the night. Tawus said, 'I cannot imagine that someone would sleep during the last part of the night!' In a Hadith recorded by Tirmidhi it mentions, "Whoever fears will travel by night and whoever travels by night will reach his destination." [Tirmidhi & Hakim]
Journeying in the last part of the night cuts short the journey of the world and the Hereafter as is mentioned in the Hadith recorded by Muslim, "When you journey, journey at the end of the night for the earth is compacted by night." [Abu Dawud]
One of the nobles said,
The burdens of journeying by night with patience bear,
Return with the morning finding you firm in obedience.
Be not faint of heart and desist not from the aspiration
For resolve dissipates in the face of despair and exasperation.
I know - and the days have practically demonstrated -
That patience has results truly meritable.
Say: Whoever strives after a matter desired
With patience accompanying him, will surely succeed.
It is reported that al-Ashtar entered upon Ali ibn Abu Talib (ra) after resting part of the night and found him standing in prayer. He said, 'Leader of the Believers, fasting by day, praying by night, and toil between the two!' When he had finished his prayer he said, 'The journey to the Hereafter is long and it needs to be cut short by journeying by night,' - this is the duljah!
The wife of Habib - Abu Muhammad al-Farisi - would wake him at night time and say, 'Awake O Habib for the path is long and our provision is paltry.The caravan of the righteous has passed ahead of us and we have been left behind!'
O sleeper by night for how long will you lie?
Awake my beloved for the Promised Time draws nigh.
For a portion of the night your Lord deify -
For sleep begets neither rest nor equanimity.
Whoever in slumber deep spends the night,
Will not have striven or arrived at the Destination right.
The Great Principle
Al-hamdulillah is the Imbursement of every Favour
Elucidation of the Meaning of Favours
Both Paradise & Deeds are from the Grace of Allah
Misery and Felicity Occur through His Justice and Mercy
Allah's Blessings can Never be Truly Repaid
One of the Greatest Blessings is Gratitude
Acknowledging the Grace of Allah
The Most Beloved Deeds to Allah
The Meaning of "Saddidu wa Qaribu"
A Noble Principle
The Ease of this Religion
The Meaning of "the beginning of the day", "the end of the day," & "a portion of the latter part of the night"
The Meaning of Moderation
Travelling the Path of Allah, Mighty and Magnificent
Deeds are by their Conclusion
The Excellence of Drawing Close to Allah
The Types of Reaching Allah
Islam, Iman, Ihsan
The Periods of Morning and Evening
Those who Hold to the World and those who Hold on to the Hereafter
The Unexpected Confrontation
The Types of Actions that will be as Scattered Dust
Sadness in the World & Misery in the Hereafter