He Included All Future Prayers in His Tefillah

The Zera Kodesh further explains the words “at that time” by saying that Moshe Rabenu opened the gates of tefillah with his prayer and left them open for all future generations to have their tefillos accepted.

The pasuk is thus saying that he included all future prayers in his tefillah. It does not say when he davened. Rather, it says that he prayed “at that time saying”, meaning that any prayer said at any future time will be included in his tefillah.