Can any man forbid the water? (Mēti to hudōr dunatai kōlūsai tiṡ). The negative mēti expects the answer No. The evidence was indisputable that these Gentiles were converted and so were entitled to be baptized. See the similar idiom in Luk 6:39. Note the article with “water.” Here the baptism of the Holy Spirit had preceded the baptism of water (Act 1:5; Act 11:16). “The greater had been bestowed; could the lesser be withheld?” (Knowling).
That these should not be baptized (tou mē baptisthēnai toutous). Ablative case of the articular first aorist passive infinitive of baptizō with the redundant negative after the verb of hindering (kōlūsai) and the accusative of general reference (toutous). The redundant negative after the verb of hindering is not necessary though often used in ancient Greek and in the Koinéš (papyri). Without it see note on Mat 19:14 and note on Act 8:36, and with it see note on Luk 4:42, note on Luk 24:16; and note on Act 14:18. Cf. Robertson, Grammar, pp. 1061, 1094, 1171. The triple negatives here are a bit confusing to the modern mind (mēti in the question, kōlūsai, to hinder or to cut off, mē with baptisthēnai). Literally, Can any one cut off the water from the being baptized as to these? Meyer: “The water is in this animated language conceived as the element offering itself for the baptism.”
As well as we (hōs kai hēmeis). The argument was conclusive. God had spoken. Note the query of the eunuch to Philip (Act 8:36).