On the Day of Pentecost, 120 folks were expecting the promise because
" And, being assembled together with them, commanded them that they should not depart from Jerusalem, but wait for the promise of the Father, which, saith he, ye have heard of me. Acts 1:4
5 For John truly baptized with water; but ye shall be baptized with the Holy Ghost not many days hence.?
"But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the
uttermost part of the earth." Acts 1:8
I don't think they knew exactly what the promise would be but they wanted to receive it. "These all
continued with one accord in prayer and supplication, with the women, and Mary the mother of Jesus, and with his brethren." v 14
and they knew this "And he said unto them, Go ye into all the world, and preach the gospel to every creature ...And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues;" Mark 16
There's a Scripture that says if you will receive, you can speak in tongues (can't remember the exact wording but will post when I find it). You know, it's like salvation in that Yahweh offers it to us but we can receive it or not.