A man entered to pray, but he did not intend that it was the Zuhr, 'Asr, or 'Isha' prayer. Is his prayer valid?

Question : If a man steps forward to pray, but he does not intend that this prayer is the Zuhr, 'Asr, Maghrib, 'Isha', or Fajr prayer, and he only intends a general prayer, does that suffice for him?

Answer : No, because the Prophet (peace and blessings be upon him) said, "Actions are only by intentions," and this man did not specify.