Sayyiduna Amr bin Abasah (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "The night prayer is to be offered two by two, and in the latter middle part of the night (supplication or worship) is most readily answered (ajwab)." He said: I asked: "Is it awjab (most binding)?" He said: "No, ajwab," meaning by that the answering (of supplication).
Ahmad recorded it; its chain contains Abu Bakr bin Abi Maryam, who is da'if (weak). He also recorded it through his route, except that in it he said: "And the latter middle part of the night is awjab (most fitting) for supplication." I asked: "Is it ajwab?" He said: "No, rather it is awjab."