A wolf is a wild dangerous animal which howls. When an individual is labelled as a 'wolf', it implies that he/she is a bad person.
The proverb 'Who keeps company with wolves will learn to howl' thus means that a person who associates with a wolf (a bad person) is very likely to become bad too.
1. Sameer's father was well aware that Ashok and his buddies spent a lot of time at gambling dens. He warned his son, "Don't get involved with them. Who keeps company with wolves, will learn to howl and you will get into trouble if you continue to hang around with them".
2. Although Rahul was a sincere politician, there were some party members who were trying to undermine him. Rahul's closest aide and long-time friend, therefore, advised him to keep away from them, saying "Who keeps company with wolves will learn to howl. It is the best to remove them from the party as they will influence others too and spoil the party image".
3. The principal decided to rusticate Mahendra from the school as his bad behaviour was leading to even good students indulging in similar behaviour and rustication would be more effective than merely warning the other students that who keeps company with wolves will learn to howl.