In Parshas Vayechi, Rashi explains that Yaakov wished to reveal to his sons when the end of Israel's exile would finally take place [ha'keitz], but the prophetic vision was closed off from him.
Rabbeinu Bachye elaborated on Rashi's words: Yaakov observed that the letters ח and ט do not appear in any of the brother's names. These are the two main letters of the word חט- sin. Yaakov took the fact that the brothers' names did not contain this word as an indication that they were clean of sin and worthy of being told when the future redemption would occur.
But then Yaakov noticed that the letters ק and ץ, which together spell the word קץ [keitz - the end of the exiles] also do not appear in their names. At that point Yaakov thought that perhaps his sons were not worthy of knowing this secret after all.
Because of his hesitation, Yaakov kept the secret closed and did not reveal the information to his sons.