well, if you mean STDs... u can still get them.
if you mean safe for you.... yes a penis is strong and wont get hurt even if its a tough a*ss.
if u mean safe for her... NOOOOO its not, even if u take it slow and lube it up good and have a small d*ck and put ur finger in first she STILL can have her butthole eventually go out when she poops, and have internal problems and bleeding, and scarring, and pain, etc.
So i wouldnt advise it, and if you do... make SURE it isnt ur wife, and its a girl who not only do u not care about its just a 1nite stand, make sure you AINT seein that girl again! lmao