Further here is testimony from the fathers, both eastern and western :
Augustine
“If that which is given has for its principle the one by whom it is given, because it did not receive from anywhere else that which proceeds from the giver, then it must be confessed that the Father and the Son are the principle of the Holy Spirit, not two principles, but just as the Father and the Son are one God . . . relative to the Holy Spirit, they are one principle” (The Trinity 5:14:15 [A.D. 408]).
“[The one] from whom principally the Holy Spirit proceeds is called God the Father. I have added the term ‘principally’ because the Holy Spirit is found to proceed also from the Son” (ibid., 15:17:29).
“Why, then, should we not believe that the Holy Spirit proceeds also from the Son, when he is the Spirit also of the Son? For if the Holy Spirit did not proceed from him, when he showed himself to his disciples after his resurrection he would not have breathed upon them, saying, ‘Receive the Holy Spirit’ [John 20:22]. For what else did he signify by that breathing upon them except that the Holy Spirit proceeds also from him” (Homilies on John 99:8 [A.D. 416]).
Tertullian
“I believe that the Spirit proceeds not otherwise than from the Father through the Son” (Against Praxeas 4:1 [A.D. 216]).
Fulgence of Ruspe
“Hold most firmly and never doubt in the least that the only God the Son, who is one person of the Trinity, is the Son of the only God the Father; but the Holy Spirit himself also one person of the Trinity, is Spirit not of the Father only, but of Father and of Son together” (The Rule of Faith 53 [A.D. 524]).
“Hold most firmly and never doubt in the least that the same Holy Spirit who is Spirit of the Father and of the Son, proceeds from the Father and the Son” (ibid., 54).
Origen
“We believe, however, that there are three persons: the Father and the Son and the Holy Spirit; and we believe none to be unbegotten except the Father. We admit, as more pious and true, that all things were produced through the Word, and that the Holy Spirit is the most excellent and the first in order of all that was produced by the Father through Christ” (Commentaries on John 2:6 [A.D. 229]).
Maximus the Confessor
"By nature the Holy Spirit in his being takes substantially his origin from the Father through the Son who is begotten (Questions to Thalassium 63 [A.D. 254]).
Gregory the Wonderworker
“[There is] one Holy Spirit, having substance from God, and who is manifested through the Son; image of the Son, perfect of the perfect; life, the cause of living; holy fountain; sanctity, the dispenser of sanctification; in whom is manifested God the Father who is above all and in all, and God the Son who is through all. Perfect Trinity, in glory and eternity and sovereignty neither divided nor estranged” (Confession of Faith [A.D. 265]).
Hilary of Poitiers
“Concerning the Holy Spirit . . . it is not necessary to speak of him who must be acknowledged, who is from the Father and the Son, his sources” (The Trinity 2:29 [A.D. 357]).
“In the fact that before times eternal your [the Father’s] only-begotten [Son] was born of you, when we put an end to every ambiguity of words and difficulty of understanding, there remains only this: he was born. So too, even if I do not g.asp it in my understanding, I hold fast in my consciousness to the fact that your Holy Spirit is from you through him” (ibid., 12:56).
Didymus the Blind
“As we have understood discussions . . . about the incorporeal natures, so too it is now to be recognized that the Holy Spirit receives from the Son that which he was of his own nature. . . . So too the Son is said to receive from the Father the very things by which he subsists. For neither has the Son anything else except those things given him by the Father, nor has the Holy Spirit any other substance than that given him by the Son” (The Holy Spirit 37 [A.D. 362]).
Epiphanius of Salamis
“The Father always existed and the Son always existed, and the Spirit breathes from the Father and the Son” (The Man Well-Anchored 75 [A.D. 374]).
Basil The Great
“Through the Son, who is one, he [the Holy Spirit] is joined to the Father, one who is one, and by himself completes the Blessed Trinity” (The Holy Spirit 18:45 [A.D. 375]).
“[T]he goodness of [the divine] nature, the holiness of [that] nature, and the royal dignity reach from the Father through the only-begotten [Son] to the Holy Spirit. Since we confess the persons in this manner, there is no infringing upon the holy dogma of the monarchy” (ibid., 18:47).
Ambrose of Milan
“Just as the Father is the fount of life, so too, there are many who have stated that the Son is designated as the fount of life. It is said, for example that with you, Almighty God, your Son is the fount of life, that is, the fount of the Holy Spirit. For the Spirit is life, just as the Lord says: ‘The words which I have spoken to you are Spirit and life’ [John 6:63]” (The Holy Spirit 1:15:152 [A.D. 381]).
“The Holy Spirit, when he proceeds from the Father and the Son, does not separate himself from the Father and does not separate himself from the Son” (ibid., 1:2:120)…