In the section in which he writes these words (GGBB, p332, fn 44), Wallace is very careful not to claim support for a view based on texts which, carefully analysed in terms of their grammar, do not support that view. Of course, this is different from saying that he does not hold to that view, but rather that, in consideration of the grammar of various passages, he will not try to bolster a case using examples that are not clear-cut. In this regard, his scholarship is exemplary.Daniel Wallace considers the interpretation given in the Expositors Greek Testament for the masculine participle (that is constructio ad sensum) and rejects it in favour of the explanation that the mas. participle is due to the personification of the three witnesses (spirit, water and blood)
Applying the same care, then, it should be noted that what Leonard has written about Wallace is, in fact, in error. Wallace does not say that the masculine participle is due to "the personification of the three witnesses (spirit, water and blood)."
Rather, he writes that
In fairness to Daniel Wallace, that is quite a different thing.the fact that the author has personified water and blood, turning them into witnesses along with the Spirit, may be enough to account for the masculine gender
In terms of the grammar, Leonard writes
Quite simply, no. How apposition and concord work differs. That's perhaps the central grammatical point: the item or items in apposition do not determine the form of the substantive to which they're in apposition. To explain this using an example in English, we might say "I saw Richard, my A, B, and C." We could substitute anything for A, B, and C - my brother, my friend, my lawyer; or my support, my strength, my cornerstone. And so if we use a pronoun for Richard, and say "I saw him, my A, B, and C" - then it is clear that the choice of gender of the pronoun - between 'her', 'him', or 'it' - is determined by Richard's gender. That is, the speaker or writer uses the gender (and number) that is applicable to whatever it is they have in mind. The appositives look after themselves - their gender doesn't matter.in 1 John 5:8 all three nouns in apposition to the participle are neuter and thus the normal rules of grammar require a neuter participle and adjective (ta marturounta and tria). Isn't this basic Greek?
The case before us is 1 John 5:7-8:
What the author has in mind is the idea of witnesses; although it is a matter of interpretation and inter-textuality, I think all who have engaged in the discussion so far, and Wallace also, consider that the author has in mind verses such as Deuteronomy 19:15b, "A matter must be established by the testimony of two or three witnesses".7 ὅτι τρεῖς εἰσιν οἱ μαρτυροῦντες, 8 τὸ πνεῦμα καὶ τὸ ὕδωρ καὶ τὸ αἷμα, καὶ οἱ τρεῖς εἰς τὸ ἕν εἰσιν.
And for the concept of witnesses, the masculine rather than the neuter is the natural choice.