Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
In Chapter 3 the Spirit addresses His testimony to the people by the mouth of Peter. God still acted in patience towards His foolish people, and with more than patience. He acts in grace towards them, as His people, in virtue of the death and intercession of Christ alas! in vain. Their unbelieving leaders silenced the word. [See Note #8] The attention of the people is attracted by a miracle that restored strength to a poor lame man, known to all who frequented the temple; and, the multitude crowding to behold him, Peter preaches Christ to them. The God of their fathers, said he, had glorified His servant Jesus, whom they had denied, when Pilate would have set Him free. They had denied the Holy One and the Just desired a murderer killed the Prince of Life; but God had raised Him from the dead. And His name, through faith, had healed the impotent man. Grace could esteem their act done as through ignorance, and that as to their rulers also. We here see the Holy Ghost responding to the intercession of Christ: "Father, forgive them, for they know not what they do!" Guilty of the ten thousand talents, the great King remits it them, sending the message of mercy which calls them to repentance. To this Peter invites them: "Repent ye, and be converted; so [See Note #9] that the time of refreshing may come from the presence of the Lord, and that he may send Jesus, whom the heaven must receive," he tells them, until the time ordained of God for the restoration which should accomplish all that the prophets had foretold. That is to say, he preaches repentance to the Jews as a nation, declaring that, on their repentance, Jesus, who had ascended up to heaven, would return; and the fulfilment of all the blessings spoken of by the prophets should take place on their behalf. The return of Jesus with this object depended (and still depends) on the repentance of the Jews. Meanwhile He remains in heaven.
Moreover Jesus was the prophet announced by Moses: and whosoever would not hear Him should be cut off from the people. His voice still sounded in especial grace by the mouth of His disciples. All the prophets had spoken of these days. They were the children of the prophets, the natural heirs of the blessings which they had announced for Israel, as well as of the promises made to Abraham of a seed in whom all nations should be blessed. To them also in consequence, God, having raised up His servant Jesus, [See Note #10] had sent Him to bless them, in turning away every one of them from his iniquities.
It is striking to see the counsels of God and their accomplishment in grace, as far as they were now being fulfilled, so clearly distinguished from the responsibility of those with whom God was dealing. In Chapter 2 Peter says, "Save yourselves from this untoward generation." God was gathering, according to His own knowledge of what was coming. In Chapter 3 he says, "God hath sent him to bless you in turning every one of you away from his iniquities." So He had, and patience still waited, though God acted in present grace according to the result known to Himself: in Jeremiah often. Had they repented, God would surely have turned from judgment, as stated also in Jeremiah.
Not "when." There is no pretence for so translating it.
This refers to the time of His life on the earth, though on His intercession there was a renewal of the mercy in testimony to a glorified Christ, who would return on their repentance.