Good companionship, choosing and having good companions is extremely important for many reasons and from many aspects.
Mankind cannot live alone; every individual must live and interact with others.
Those people who you sit with and make your friends are inevitably going to fall into one of two categories. Either they are going to be good individuals - who guide and encourage you towards what is good and help you to accomplish that which Allah has ordered, or they are going to be bad - encouraging you to do what is pleasing to Shaytaan, that which misleads you, and leads you to the Hell-Fire.
There are many ahaadeeth which speak of its virtue, such as the words of the Prophet (peace and blessings of Allah be upon him): When the Muslim visits his (sick) Muslim brother, he is harvesting the fruits of Paradise until he returns.
"One of the greatest blessings of Islâm is it's admirable success in
creating strong, warm, rich and durable bonds of love and brotherhood
between man. It is this blessing of love and brotherhood which is the
greatest source of sustenance and nourishment for man, but few of us can
honestly say that we have experienced true brotherhood."