First hour: after Salat-ul fajr:
Our prophet said (saw): the one whoever prays salat-ul fajr in Jamaah and sits after prayer to read Athkaar until sunrise, then prays 2 rakateen, it is rewarded as accomplishing hajj and omra. Second hour: last hour before Iftaar:
Once Musa (a.s.) asked Allah (Subhaan’oTa’la) : O Allah ! You have granted me the honor and privilege of talking to you directly, have you given this privilege to any other person? Allah Ta’ala replied, O Musa during the last period I am going to send an Ummat, who will be the Ummat of Mohammed (saw) with dry lips, parched toungues, emaciated body with eyes sunken deep into their sockets, with livers dry and stomachs suffering the pangs of hunger, will call out to me (in dua) they will be much closer to me than you O Musa! While you speak to me there are 70000 veils between you and me but at the time of iftaar there will not be a single Veil between me and the fasting Umaati of Muhammed (saw), O Musa I have taken upon myself the responsibility that at the time of Iftaar I will never refuse the dua of a fasting person!
Our prayers in this hour are all granted inshaAllah, therefore we should never waste it by watching TV or preparing food. Third hour: late night hours (Suhoor time)
It is preferred to spend this hour with Esteghfar and prayers (e.g. Tahajjud).