In Hadith Shareef, Rasulullah (sallallahu 'alayhi wa alihiwa sallam) said that his descendants are like the boat of Hazrat Nooh ('alayhis salam), so whoever approaches this boat, is saved, whoever cuts from it, is perished and misguided.
Allah has chosen the descendants of Sayyiduna Ibraheem ('alayhis salaam), precisely that of Sayyiduna 'Ismaaeel ('alayhis salaam), more precisely that of our Beloved Prophet (sallallahu 'alayhi wa alihi wa sallam) over mankind. The Qur'an asks us to hold on the Rope of Allah so as to not be divided. The Rope of Allah, has several interpretations, one interpretation is that the Rope of Allah is AhlulBayt (Family of Beloved Prophet sallallahu 'alayhi wa alihi wa sallam). So as long as you keep yourself connected with them, you are in right hands.
In another Hadith Shareef, Rasulullah (sallallahu 'alayhi wa alihi wasallam) said that his companions (Sahaba) are like stars, if you follow any one of them, you'll be guided.
Yes, some stars are brighter than the others, and as known there are 4 big and known stars. Similarly, Sahabas have superiority each other among the Sahabas, 4 are great, that are the 4 Khalifaa: Hadhrat Abu Bakr Siddeeq, Hadhrat 'Umar Farooq, Hadhrat 'Uthmaan Ghani, and Hadhrat 'Ali Wali (radi Allahu ta'ala 'anhum wa karam Allahu wajhu)
In a Hadith, its said that Hadhrat Abu Bakr (radi Allahu 'anhu) is the foundation, Hadhrat 'Umar (radi Allahu 'anhu) is the wall, Hadhrat 'Uthmaan (radi Allahu 'anhu) is the roof, and the door is Hadhrat 'Ali (karam Allahu wajhu). And in some places, Rasulullah (sallallahu 'alayhi wa alihi wa sallam) said that I am the City of Knowledge and 'Aliy is its Door (karam Allahu wajhu)
We, the Ummah, are in a journey. Our mode of transport is the boat (Ahlul Bayt radi Allahu 'anhum), we have to reach a Destination and our map to guide ourselves to that Destination are the stars (Sahaba-radi Allahu 'anhum). This resumes what we mentioned from the begining. So, do not leave any of these two or else you won't reach the Destination.
If you only look at the stars without getting on the boat, you'll remain where you are, no progress. If you climb on the boat, but do not take help from the stars, you wont arrive at your Destination.
One question is asked. Why Ahl e Bayt has been referred as boat?
The answer is that, in the sea of religion, there are many dangers and waves, so to tackle these waves, Ahl e Bayt has been made a boat
[Taken from the 'Ulema]