Translation of the verse 26 from Surah Al-Insan : Number of verses 31 - - page 580 - Part 29.
And during night, prostrate yourself to Him (i.e. the offering of Maghrib and 'Isha' prayers), and glorify Him a long night through (i.e. Tahajjud prayer).
And during the night prostrate to Him and exalt Him a long [part of the] night.
(76:26) and prostrate yourself before Him at night, and extol His Glory during the long watches of the night. *30
*30) The rule followed in the Qur'an is that wherever the Muslims have been exhorted to show patience against the disbelievers, immediately after it they have been commanded to remember Allah much and to observe the Prayer, which automatically implies that the power needed to meet the resistance of the enemies of the Truth in the way of truth faith can be obtained only by this means. To remember Allah morning and evening may also imply remembering Allah always but when the command to remember Allah at specific times is given, it implies the salat (Prayer). In this verse, bukrah means the morning and asil the time from the sun's decline till sunset, which obviously covers the Zuhr and the Asr times. Night starts after sunset;. therefore, the command "to prostrate yourself in the night" would apply to both the Maghrib and the `Isha' Prayers. Then, the command "to glorify Allah in the long hours of night", clearly points to the time of the Tahajjud Prayer. (For further explanation, see E.N.'s 92 to 97 of Bani Isra'il, E N. 2 of AI-Muzzammil). This also shows that these very have been the Prayer times in Islam from the beginning. However, the command making the Prayer obligatory five times a day with fixed tunes and number of rak ahs was given on the occasion of mi`raj (ascension).
Source : Al-Insan Verse 26: And during the night prostrate to Him and exalt Him a long [part of the] night.