Mateo 18:12

Leave the ninety and nine

(αφησε τα ενενηκοντα εννεα επ τα ορη κα πορευθεις ζητε το πλανωμενον?). This is the text of Westcott and Hort after BL, etc. This text means: "Will he not leave the ninety and nine upon the mountains and going does he not seek (change to present tense) the wandering one?" On the high pastures where the sheep graze at will one has wandered afield.

See this parable later in Lucas 15:4-7. Our word "planet" is from πλαναομα, wandering (moving) stars they were called as opposed to fixed stars. But now we know that no stars are fixed. They are all moving and rapidly.