FIRST, by the testimonies of sacred Scripture, which attribute to God greatness and excellence above all created things (Job 36:26 and 37:23; Psalm 48:1 and 95:3 and 96:4 and 97:9 and 99:2 and 145:3; Titus 2:13 and elsewhere everywhere).
SECOND, from God's highest goodness. Such goodness is necessarily undefective for eternities, and therefore infinite: since every finite goodness necessarily falls short of the highest goodness. From which Gregory of Nyssa (On the Making of Man, chapter 1) teaches that God is good, surpassing every good which is comprehended by understanding and thinking — that is, infinite.
Latin
PRIMO, sacrae Scripturae testimoniis, quae Deo magnitudinem & excellentiam supra omnes res creatas attribuunt, Job. 36.26 & 37.23; Psal. 48.2 & 95.3 & 96.4 & 97.9 & 99.2 & 145.3; Tit. 2.13 & alibi passim. SECUNDO, a summa Dei bonitate. Talis bonitas necessario est aeternis indefecta, adeoque infinita: cum omnis finita bonitas necessario deficiat a summa bonitate. Unde Gregorius Nyssenus libro de opificio hominis cap. 1. docet, Deum esse bonum, omne bonum, quod intelligendo cogitandoque comprehenditur, exsuperans, hoc est, infinitum.