Mat_21:25  The baptism of John, whence was it? from heaven, or of men? And they reasoned with themselves, saying, If we shall say, From heaven; he will say unto us, Why did ye not then believe him?

baptism:  Mat_3:1-12, Mat_11:7-15, Mat_17:12, Mat_17:13, Mar_1:1-11, Mar_11:27-33, Luk_1:11-17, Luk_1:67-80, Luk_3:2-20, Luk_7:28-35, Joh_1:6, Joh_1:15, Joh_1:25-34, Joh_3:26-36

Why:  Luk_20:5, Joh_3:18, Joh_5:33-36, Joh_5:44-47, Joh_10:25, Joh_10:26, Joh_12:37-43, 1Jo_3:20