Bilaam’s unique power to curse lay in his ability to pinpoint the instant each day when Hashem is “angry.” By cursing at that moment, Bilaam knew that Hashem’s wrath would allow the curse to take effect.
But how much can one curse in a brief instant? The commentaries say that as long as he began at that instant, he could continue as long as he wanted and he would take along that power.
From this explanation we learn a key lesson about Tefila B’Tzibbur, davening with a quorum of ten: Ideally, when the tzibbur begins Shemona Esrai, one should begin with them. He should even hurry through or skip earlier parts to start with them.
The best way to “begin with the Tzibbur” is to finish the bracha of Go’al Yisrael with the Shliach Tzibbur or just before, then begin Hashem S’fasai Tiftach, so he doesn’t have to say Amen (MB 66:35).
For the most part, one is considered to have begun with the tzibbur if he begins while ten people are still in the first bracha of Shemona Esrai, or at least before Ha’Keil HaKadosh.
Others say that as long as ten people are still davening Shemona Esrai one has fulfilled his obligation to daven Tefila B’Tzibbur (and his prayers will be accepted even if he doesn’t have 100% concentration, unlike when he davens alone.)
Starting Shemona Esrai with the Shliach Tzibbur is a matter of discussion. The Rem”a says to wait until after Kedusha, but others say that starting with the Shat”z would constitute Tefila B’Tzibbur.
