PTHor 47.a:38[2] :שרי טפח בחדא ידיה אמ׳ ליה ובחדא ידא טפחין‏ : he began to clap with one hand; he said to him: can one clap with one hand?
See the entire entry for ṭpḥ vb. to spread out; strike with the fist