He stabbed him on his neck.
Basil visits Dorian to express his concern about Dorian's behavior at the opera. Basil is worried about the influence Lord Henry may be having on Dorian and wants to make sure Dorian is not being negatively influenced by him.
Chapter 13 in the 1891 version, chapter 11 in the 1890 version.
Lord Henry contrasts Basil's reserved and introspective nature with Dorian's youthful charm, vitality, and impressionability. Basil is seen as more cautious and moderate, while Dorian is depicted as adventurous and easily influenced by external factors.
Basil does not want to exhibit his portrait of Dorian Gray because he feels it reveals too much of his own feelings and emotions. He believes the painting shows his innermost thoughts and secrets, which he is not comfortable sharing with the world. Additionally, Basil worries that the painting's beauty might overshadow his other works and that it represents a departure from his usual style.
He is (properly) afraid that Harry will corrupt Dorian.
On a party.
In "The Picture of Dorian Gray" by Oscar Wilde, Lord Henry, Dorian Gray, and Basil Hallward are present for lunch at Lord Henry's aunt's home. Lord Henry and Basil are discussing Dorian Gray, who is the subject of Basil's portrait.
He tells him to pray together to regain his innocence.
He was afraid the picture shows his secret feelings for Dorian.
Dorian has the innocence of ignorance, and is easily impressible. Basil has mature, stable morals, which resist even the almighty charms of Henry. Henry compared their looks: Basil's "rugged strong face and coal-black hair" and Dorian, who looks like he was "made of ivory and rose petals".
He admits Basil is a good man, although weak and afraid of life.