“In that hour Jesus rejoiced in spirit, and said, I thank thee, O Father, Lord of heaven and earth, that thou hast hid these things from the wise and prudent, and hast revealed them unto babes: even so, Father; for so it seemed good in thy sight.”
At that time Jesus, full of joy through the Holy Spirit, said, I praise you, Father, Lord of heaven and earth, because you have hidden these things from the wise and learned, and revealed them to little children. Yes, Father, for this is what you were pleased to do — full of joy through the Holy Spirit is Luke's unique description of the Spirit-filled rejoicing. The thanksgiving addresses the pattern of revelation: hidden from the wise and learned (those confident in their own understanding), revealed to little children (the humble, the dependent). This is what you were pleased to do: the sovereignty of the Father in revelation is affirmed.
Church Fathers on Luke 10:21
As a loving father rejoices to see his sons do right, so Christ also rejoices that His Apostles were made worthy of such good things. Hence it follows, In that hour, &c.
He saw in truth that through the operation of the Holy Spirit, which He gave to the holy Apostles, the acquisition of many would be made, (or that many would be brought to the faith.) He is said therefore to have rejoiced in the Holy Spirit, that is, in the results which came forth through the Holy Spirit. For as one who to be mankind He considered the conversion of sinners to be a subject for rejoicing, for which He gives thanks. As it follows, I give thanks to you, O…
Confessing does not always signify penitence, but also thanks airing, as is frequently found in the Psalms.