Baptized with water (ebaptisen hudati) and with the Holy Ghost (en pneumati baptisthēsesthe hagiōi). The margin has “in the Holy Ghost” (Spirit, it should be). The American Standard Version renders “in” both with “water” and “Holy Spirit” as do Goodspeed (American Translation) and Mrs. Montgomery (Centenary Translation). John’s own words (Mat 3:11) to which Jesus apparently refers use en (in) both with water and Spirit. There is a so-called instrumental use of en where we in English have to say “with” (Rev 13:10 en machairēi, like machairēi, Act 12:2). That is to say en with the locative presents the act as located in a certain instrument like a sword (Robertson, Grammar, pp. 589f.). But the instrumental case is more common without en (the locative and instrumental cases having the same form). So it is often a matter of indifference which idiom is used as in Joh 21:8 we have tōi ploiariōi (locative without en). They came in (locative case without en) the boat. So in Joh 1:31 en hudati baptizōn baptizing in water. No distinction therefore can be insisted on here between the construction hudati and en pneumati (both being in the locative case, one without, one with en). Note unusual position of the verb baptisthēsesthe (future passive indicative) between pneumati and hagiōi. This baptism of the Holy Spirit was predicted by John (Mat 3:11) as the characteristic of the Messiah’s work. Now the Messiah himself in his last message before his Ascension proclaims that in a few days the fulfilment of that prophecy will come to pass. The Codex Bezae adds here “which ye are about to receive” and “until the Pentecost” to Act 1:5.
Not many days hence (ou meta pollas tautas hēmeras). A neat Greek idiom difficult to render smoothly into English: “Not after many days these.” The litotes (not many=few) is common in Luke (Luk 7:6; Luk 15:13; Act 17:27; Act 19:11; Act 20:12; Act 21:39; Act 28:14; Act 28:2). The predicate use of tautas (without article) is to be noted. “These” really means as a starting point, “from these” (Robertson, Grammar, p. 702). It was ten days hence. This idiom occurs several times in Luke (Luk 24:21; Act 24:21), as elsewhere (Joh 4:18; 2Pe 3:1). In Luk 2:12 the copula is easily supplied as it exists in Luk 1:36; Luk 2:2.