Did Jesus Teach Perseverence/Once Saved Always Saved? No
Let's look at Jesus's own words and see if he taught of believed that once a Christian believed and trusted in him they could never fall away.
Jesus the Vine
John 15:1-5
1 “I am the true vine, and My Father is the vinedresser. 2 Every branch in Me that does not bear fruit, He takes away; and every branch that bears fruit, He prunes it so that it may bear more fruit. 3 You are already clean because of the word which I have spoken to you. 4 Abide in Me, and I in you. As the branch cannot bear fruit of itself unless it abides in the vine, so neither can you unless you abide in Me. 5 I am the vine, you are the branches; he who abides in Me and I in him, he bears much fruit, for apart from Me you can do nothing.
Christians are the Branches, and Jesus teaches us that His Father is the Vine Dresser and he prunes back so that there is more growth, The Branches can not bear fruit unless they abide in him.
John 15:6
6 If anyone does not abide in Me, he is thrown away as a branch and dries up; and they gather them, and cast them into the fire and they are burned.
Yes, Jesus gives us a clear warning, but he also gives assurance and a promise that if we abide in him and his words abide in us we know he will never forsake us.
John 15:7-11
7 If you abide in Me, and My words abide in you, ask whatever you wish, and it will be done for you. 8 My Father is glorified by this, that you bear much fruit, and so prove to be My disciples. 9 Just as the Father has loved Me, I have also loved you; abide in My love. 10 If you keep My commandments, you will abide in My love; just as I have kept My Father’s commandments and abide in His love. 11 These things I have spoken to you so that My joy may be in you, and that your joy may be made full.
Do Jesus clear words on Perserverance abide in you, or do they get tossed aside because your Doctrine tells you otherwise?
Let's look at another clear example.
Matthew 5:13
13 “You are the salt of the earth; but if the salt has become tasteless, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled under foot by men.
Jesus gives us these clear warnings, so that we can be on alert and abide in him. He did not come to tickle your ears.