Sayyiduna Abu al-Darda' (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "Allah Almighty says: O son of Adam, do not fall short of four rak'ahs in the early part of the day (i.e. do offer them), and I will suffice you until the last part of it (the day)."
Ahmad recorded it, and its narrators are thiqat (trustworthy).