Riyad-us-Saliheen 849
'Abdullah bin Salam (May Allah be pleased with him) reported: I heard the Messenger of Allah (PBUH) saying, "O people, exchange greetings of peace (i.e., say: As-Salamu 'Alaikum to one another), feed people, strengthen the ties of kinship, and be in prayer when others are asleep, you will enter Jannah in peace."
[At-Tirmidhi]
All these habits and practices are indispensable to a believer because each one of them leads to Jannah with the first people to enter it without being punished in Hell first.