What is the Scriptural support for the Catholic Church's "depositum fidei"? What is the biblical basis that there is a thing which the Catholic Church terms as "depositum fidei"?

Depositum fidei, i.e the Sacred deposit of the faith that consists of Sacred Scripture and Holy Tradition that was mentioned in this answer and this.
The term "depositum fidei" is just another way of saying Revelation.

St. Paul charges St. Timothy to keep and preserve Revelation (1 Timothy 6:20):


  O Timothy, keep the depositum, avoiding the profane novelties of voices, and oppositions of falsely called knowledge.


The original Rheims New Testament commentary says:


  
  Depositum. ] The whole doctrine of our Christianity being taught by the Apostles, and delivered to their successors, and coming down from one Bishop to another, is called the Depositum, as it were a thing laid into their hands, and committed unto them to keep. Which because it passeth from hand to hand, from age to age, from Bishop to Bishop without corruption, change, or alteration, is all one with Tradition, and is the truth given unto the holy Bishops to keep, and not to laymen. See the notable discourse of Vincentius Lirensis upon this text li. cont. profan. har. Novationes. And it is for this great, old, and known treasure committed to the Bishop's custody, that St. Irenaeus calleth the Catholic Church Depositorium dives, the rich treasury of truth. li. 3 c. 4. And as Clement Alexandrinus writeth li. 2 Strom. this place maketh so much against all Heretics who do change this Depositum, that for it only such man in his days denied this Epistle. The Heretics of our days challenge also the truth, and say it is the old truth but they leap 14 or 15 hundred years from it over men's heads to the Apostles.  But we call for the Depositum, and ask them in whose hands that truth which they pretend, was laid up and how it came down to them. For it cannot be Apostolical, unless it were Depositum in some Timothy's hand, so to continue from one Bishop to another until our time to the end.
  




Please see also:


  Matt 28:19-20 (RSVCE) 19 Go therefore and make disciples of
  all nations, baptizing them in the name of the Father and of the Son
  and of the Holy Spirit, 20 teaching them to observe all that I
  have commanded you; and lo, I am with you always, to the close of the
  age.”


And


  2 Thess 2:14-16 (RSVCE) 14 To this he called you through our
  gospel, so that you may obtain the glory of our Lord Jesus Christ.
  15 So then, brethren, stand firm and hold to the traditions which you were taught by us, either by word of mouth or by letter.
  
  16 Now may our Lord Jesus Christ himself, and God our Father, who loved us and gave us eternal comfort and good hope through grace,


And


  Gal 1:7-9 (RSVCE) 7 not that there is another gospel, but
  there are some who trouble you and want to pervert the gospel of
  Christ. 8 But even if we, or an angel from heaven, should preach
  to you a gospel contrary to that which we preached to you, let him be
  accursed. 9 As we have said before, so now I say again, If any one
  is preaching to you a gospel contrary to that which you received, let
  him be accursed.


Even the Angels and the Apostles are not to depart from the deposit of faith.