After Rabbi Elazar recites the Sh'ma and says his prayers, Rabbi Yitzchak begins a discussion of the proper times to pray. Before commencing a journey, for example, we should first consult God and offer prayer. We should also offer prayers at midnight and in the morning after the sun rises, but not in the darkness of early morning, since this is a time when husband and wife are bound up as one in the secret of union.
In truth, prayers are non-material cables that transmit specific spiritual influences to our souls. Different influences are "broadcast" at intervals during the earth's rotation and orbit around the sun. The ancient sages understood these timetables and constructed the appropriate "cables" in the form of prayers. Reading this passage helps align and tune our prayers to their highest frequency, maximizing their strength and effectiveness.