“And as he passed by, he saw Levi the son of Alpheus sitting at the receipt of custom, and said unto him, Follow me. And he arose and followed him.”
As he walked along, he saw Levi son of Alphaeus sitting at the tax collector's booth. Follow me, Jesus told him, and Levi got up and followed him — the call of Levi mirrors the call of Simon and Andrew (Mark 1:16–18): Jesus sees, Jesus calls, the called one leaves immediately. Levi son of Alphaeus is almost certainly the Matthew of Matthew 9:9. Tax collectors (telōnai) collected tariffs on goods crossing regional boundaries; they were despised for their collaboration with Rome, their potential for extortion, and their ritual impurity from constant contact with Gentile goods and money. Jesus' call of a tax collector as a disciple is as socially provocative as any miracle in the Gospel.
Church Fathers on Mark 2:14
After that the Lord taught at Capernaum, He went to the sea, that He might not only set in order the life of men in towns, but also might preach the Gospel of the kingdom to those who dwelt near the sea, and might teach them to despise the restless motions of those things which pass away like the waves of the sea, and to overcome them by the firmness of faith.
Or else, after the miracle, He goes to the sea, as if wishing to be alone, but the crowd runs to Him again, that thou mightest learn, that the more thou fliest from glory, the more she herself pursues thee; but if thou followest her, she will fly from thee. The Lord passing on from thence called Matthew.
Thus then Levi, which means Appointed, followed from the custom-house of human affairs, the Word, Who says, 'He who doth not quit all that he has, cannot be My disciple.'