A.T. Robertson Commentary Luke 24:44

"And he said unto them, These are my words which I spake unto you, while I was yet with you, that all things must needs be fulfilled, which are written in the law of Moses, and the prophets, and the psalms, concerning me." — Luke 24:44 (ASV)

While I was yet with you (ετ ων συν υμιν). Literally,

Being yet with you . The participle ων takes the time of the principal verb.