I agree with those others have already mentioned. There is one saint I really like for his faithful witness and brevity and that is St Thalassios the Lybian who was a friend of St. Maximos the Confessor. His Trinitarian statements are so concise yet must be pondered ( although he was undoubtedly helping us to understand plainly).
For ex.
91. Just as the single essence of the Godhead is said to exist in three Persons, so the Holy Trinity is confessed to have one essence.
92. We regard the Father as unoriginate and as the source: as unoriginate because He is unbegotten, and as the source because He is the begetter of the Son and the sender forth of the Holy Spirit, both of whom are by essence from Him and in Him from all eternity.
93. Paradoxically, the One moves from itself into the Three and yet remains One, while the Three return to the One and yet remain Three.
94. Again, the Son and the Spirit are regarded as not unoriginate, and yet as from all eternity. They are not unoriginate because the Father is their origm and source: but They are eternal in that They coexist with the Father, the one begotten by Him and the other proceeding from Him from all eternity.
90. The single divinity of the Trinity is undivided and the three Persons of the one divinity are unconfused.
96. The individual characteristics of the Father are described as unoriginateness and unbegottenness: of the Son, as co-presence in the source and as being begotten by it; and of the Holy Spirit, as co-presence in the source and as proceeding from it. The origin of the Son and Holy Spirit is not to be regarded as temporal: how could it be? On the contrary, the term 'origin' indicates the source from which Their existence is eternally derived, as light from the sun For They originate from that source according to Their essence, although They are in no sense inferior or subsequent to it.
97. Each Person preserves His individual characteristics im-mutably and irremovably; and the common nature of Their essence, that is to say. Their divinity, is indivisible.
98. We confess Units- in Trinits' and Trinity in Unity, divided but without division and united but with distmctions.
99. The Father is the sole origm of all things. He is the origin of the Son and the Spirit as Their begetter and source. coetemal, co-infinite, limitless, coessential and undivided. He is the origin of created things, as the one who produces, provides for, and judges them through the Son in the Holy Spirit. 'For all things are from Him and through Him, and have Him as their goal. To Him be glory throughout the ages. Amen' (Rom. I 1 :36).
100. Again, the Son and the Holy Spirit are said to be coetemal with the Father, but not co-unoriginate with Him. They are coetemal in that They coexist with the Father from eternity; but They are not co-unoriginate in that They are not without source: as has already been said. They are derived from Him as the light from the sun, even though They are not inferior or subsequent to Him. They are also said to be unoriginate in the sense that They do not have an origin in time. If this were not the case. They would be thought of as subject to time, whereas it is from Them that time itself derives. Thus They are unoriginate not with regard to Their source, but with regard to time. For They exist prior to, and transcend, all time and all the ages; and it is from Them that all time and all the ages are derived, together with everything that is in time and in the ages. This is because They are, as we said, coetemal with the Father; to Him, with Them, be glory and power through all the ages. Amen.
These are from his third set of “century” statements in the Philokalia vol.2 . If one reads his writings just take note that he was a monastic & a couple times he mentioned penance involving remedy like strict fasting. An equivalent for most of us should be something like maybe substituting a salad & sandwich for a sumptuous meal & giving the difference to a soup kitchen ( for ex).
St. Thalassios brief info:
www.johnsanidopoulos.com
His writings:
Thalassios the Libyan: On Love, Self-control and Life in Accordance with the Intellect
