Reference for Bava Metzia 58:2
אמר רב יהודה אמר שמואל הלכה כר' טרפון ביד רחבה הוה ליה הנהו זוזי דיתמי אתא לקמיה דרב יוסף אמר ליה מהו לאשתמושי בגוייהו א"ל הכי אמר רב יהודה אמר שמואל הלכה כר' טרפון
Rab. Judah said in Samuel's name: The <i>halachah</i> is as R. Tarfon. Rehabah had in his charge an orphan's money. He went before R. Joseph and enquired. 'May I use it?' He replied, 'Thus did Rab Judah say in Samuel's name, The <i>halachah</i> is as R. Tarfon. Thereupon Abaye protested, But was it not stated thereon: R. Helbo said in R. Huna's name: This refers only to the purchase price of a lost article, since he took trouble therein,<span class="x" onmousemove="('comment',' Before selling it he had to look after it for a certain time; therefore he is now privileged to use the money. ');"><sup>2</sup></span>