Q. When did Jesus become filled with the Holy Spirit?
The Bible does not tell us specifically when Jesus became filled with the Holy Spirit. However, my answer to your question would be that he was likely filled with the Spirit from the moment of his conception.
I say this for two reasons. First, the angel Gabriel told Zechariah that his son, who grew up to be John the Baptist, would be “filled with the Holy Spirit even from his mother’s womb.” John himself said that Jesus was greater than he was, and I cannot imagine that Jesus would not have had at least the same kind of filling with the Spirit that John did.
The second reason why I think that Jesus was filled with the Holy Spirit from the time of his conception is the prophecy that Isaiah gave about the coming Messiah. Isaiah said:
For to us a child is born,
to us a son is given;
and the government shall be upon his shoulder,
and his name shall be called
Wonderful Counselor, Mighty God,
Everlasting Father, Prince of Peace.
Of the increase of his government and of peace
there will be no end,
on the throne of David and over his kingdom,
to establish it and to uphold it
with justice and with righteousness
from this time forth and forevermore.
Isaiah went on to say:
There shall come forth a shoot from the stump of Jesse,
and a branch from his roots shall bear fruit.
And the Spirit of the Lord shall rest upon him,
the Spirit of wisdom and understanding,
the Spirit of counsel and might,
the Spirit of knowledge and the fear of the Lord.
And his delight shall be in the fear of the Lord.
This suggests to me that this filling with the Spirit was to be true of the promised child from the time that he was born, and so arguably from the time of his conception. And Christians understand Jesus to have fulfilled this prophecy of the coming Messiah.
It is true that the gospels say that when Jesus was baptized, “he saw the Spirit of God descending like a dove and coming to rest on him.” But this was not necessarily the moment at which Jesus was first filled with the Spirit. Rather, I think it was visible testimony from God that Jesus was indeed the one about whom Isaiah prophesied that “the Spirit of the Lord shall rest upon him.” This is what confirmed for John the Baptist, for example, that Jesus was indeed the Messiah. John told the crowds, “I saw the Spirit descend from heaven like a dove, and it remained on him. I myself did not know him, but he who sent me to baptize with water said to me, ‘He on whom you see the Spirit descend and remain, this is he who baptizes with the Holy Spirit.’ And I have seen and have borne witness that this is the Son of God.”
Good Question 