Isaac was born into a prominent Sephardic Portuguese merchant family in 1798 in Amsterdam, Netherlands and he received a Jewish education. Although his father outwardly followed the Sephardic customs, he was not orthodox.
Isaac was a very talented man, who knew how to relate the developments in society, politics, church, science and art to Biblical fundamentals. He spoke ten languages and at only 23 years old, he had a degree in language and literature and law. He strongly influenced politics, acted counter to false doctrines and held, for decades, Bible studies every Sunday night. A number of which have been published.
His early years
As a teenager, Isaac believed that Jesus was a light that rose from Israel to light the Gentiles. The history lessons in Latin school showed him that the books of Moses were historically authentic. This was a reason for him to believe in the Divine nature of the Old Testament. Later he started to see that the history of Israel could only be understood by looking at the chosen people as a nation of God.
The prophecies fulfilled
When Isaac was 22 years old, he started to read the New Testament. This was a result from his contact with the greatest poet from his time, Bilderdijk. This man explained to him the promises that God gave to Abraham, Isaac and Jacob. He also showed him that a Christian has the same expectation as the Jews, namely that in God’s time the Messiah will rule as a King on the throne of David.
Isaac, himself, wrote about his conversion, “I began to read the New Testament. I read that unspeakably sublime and blessed word, ‘In the beginning was the Word, and the Word was with God, and the Word was God, and the Word was made flesh’ (John 1:1,14). I began to feel an abhorrence of sin for which the Saviour Himself, manifested in the flesh, had suffered the death of the cross. I realised the fulfilment of the prophecies of Isaiah 11, 53, 61, and in Psalms 22 and 110. I adored, I believed and slowly this faith worked on my conscience and my behaviour changed. Religion was no longer merely a sublime speculation, or a great national interest. I found that I must become the property of Jesus Christ, that I must live to Him, and by Him.”
Isaac da Costa, his wife Hannah Belmonte and his friend Abraham Capadose were baptized in 1822 in Leiden.
Themes in his works
In his poems, writings and preaching there are distinctive recurrent themes of the Holy Trinity; the God and man being of Jesus; His conciliatory suffering and dying; the promises for Israel and the Second Coming of Jesus in glory. On the subject Israel, he expounded this subject in separate books and propositions. Isaac kept speaking about the fact that the Old Testament is full of prophesies about the national restoration of Israel. Israel will repent as a nation and God will adopt them again. Jesus Christ was revealed in the gospel of Luke as the King of Israel to reign over the house of Jacob (Luke 1:26-33). As an assignment to the Church of Jesus Christ he saw the love and prayer for Israel, the search of the prophecies about Israel and the preaching of the Gospel to Israel.